Java中hashCode的作用-优快云博客

本文深入探讨了哈希码的概念及其在哈希表中的应用，解释了哈希码与对象相等性的关系，同时展示了如何通过哈希码优化数据查找效率。文章还通过示例代码演示了如何在类中重写哈希码和equals方法以提高集合框架的性能。

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以下是关于HashCode的官方文档定义：

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 hashcode方法返回该对象的哈希码值。支持该方法是为哈希表提供一些优点，例如，java.util.Hashtable提供的哈希表。 
  
 hashCode的常规协定是： 
 在Java应用程序执行期间，在同一对象上多次调用hashCode方法时，必须一致地返回相同的整数，前提是对象上equals比较中所用的信息没有被修改。从某一应用程序的一次执行到同一应用程序的另一次执行，该整数无需保持一致。 
 如果根据equals(Object)方法，两个对象是相等的，那么在两个对象中的每个对象上调用hashCode方法都必须生成相同的整数结果。 
 以下情况不是必需的：如果根据equals(java.lang.Object)方法，两个对象不相等，那么在两个对象中的任一对象上调用hashCode方法必定会生成不同的整数结果。但是，程序员应该知道，为不相等的对象生成不同整数结果可以提高哈希表的性能。 
 实际上，由Object类定义的hashCode方法确实会针对不同的对象返回不同的整数。（这一般是通过将该对象的内部地址转换成一个整数来实现的，但是JavaTM编程语言不需要这种实现技巧。） 
  
 当equals方法被重写时，通常有必要重写hashCode方法，以维护hashCode方法的常规协定，该协定声明相等对象必须具有相等的哈希码。 

以上这段官方文档的定义，我们可以抽出成以下几个关键点：

1、hashCode的存在主要是用于查找的快捷性，如Hashtable，HashMap等，hashCode是用来在散列存储结构中确定对象的存储地址的；

2、如果两个对象相同，就是适用于equals(java.lang.Object) 方法，那么这两个对象的hashCode一定要相同；

3、如果对象的equals方法被重写，那么对象的hashCode也尽量重写，并且产生hashCode使用的对象，一定要和equals方法中使用的一致，否则就会违反上面提到的第2点；

4、两个对象的hashCode相同，并不一定表示两个对象就相同，也就是不一定适用于equals(java.lang.Object) 方法，只能够说明这两个对象在散列存储结构中，如Hashtable，他们“存放在同一个篮子里”。

再归纳一下就是hashCode是用于查找使用的，而equals是用于比较两个对象的是否相等的。以下这段话是从别人帖子回复拷贝过来的：

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 1.hashcode是用来查找的，如果你学过数据结构就应该知道，在查找和排序这一章有 
 例如内存中有这样的位置 
 01234567 
 而我有个类，这个类有个字段叫ID,我要把这个类存放在以上8个位置之一，如果不用hashcode而任意存放，那么当查找时就需要到这八个位置里挨个去找，或者用二分法一类的算法。 
 但如果用hashcode那就会使效率提高很多。 
 我们这个类中有个字段叫ID,那么我们就定义我们的hashcode为ID％8，然后把我们的类存放在取得得余数那个位置。比如我们的ID为9，9除8的余数为1，那么我们就把该类存在1这个位置，如果ID是13，求得的余数是5，那么我们就把该类放在5这个位置。这样，以后在查找该类时就可以通过ID除8求余数直接找到存放的位置了。 
  
 2.但是如果两个类有相同的hashcode怎么办那（我们假设上面的类的ID不是唯一的），例如9除以8和17除以8的余数都是1，那么这是不是合法的，回答是：可以这样。那么如何判断呢？在这个时候就需要定义equals了。 
 也就是说，我们先通过hashcode来判断两个类是否存放某个桶里，但这个桶里可能有很多类，那么我们就需要再通过equals来在这个桶里找到我们要的类。 
 那么。重写了equals()，为什么还要重写hashCode()呢？ 
 想想，你要在一个桶里找东西，你必须先要找到这个桶啊，你不通过重写hashcode()来找到桶，光重写equals()有什么用啊 

最后，我们来看一个具体的示例吧，

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 publicclassHashTest{ 
 privateinti; 
  
 publicintgetI(){ 
 returni; 
 } 
  
 publicvoidsetI(inti){ 
 this.i=i; 
 } 
  
 publicinthashCode(){ 
 returni%10; 
 } 
  
 publicfinalstaticvoidmain(String[]args){ 
 HashTesta=newHashTest(); 
 HashTestb=newHashTest(); 
 a.setI(1); 
 b.setI(1); 
 Set<HashTest>set=newHashSet<HashTest>(); 
 set.add(a); 
 set.add(b); 
 System.out.println(a.hashCode()==b.hashCode()); 
 System.out.println(a.equals(b)); 
 System.out.println(set); 
 } 
 } 

这个输出的结果：

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 true 
 false 
 [com.ubs.sae.test.HashTest@1,com.ubs.sae.test.HashTest@1] 

以上这个示例，我们只是重写了hashCode方法，从上面的结果可以看出，虽然两个对象的hashCode相等，但是实际上两个对象并不是相等；，我们没有重写equals方法，那么就会调用object默认的equals方法，是比较两个对象的引用是不是相同，显示这是两个不同的对象，两个对象的引用肯定是不定的。这里我们将生成的对象放到了HashSet中，而HashSet中只能够存放唯一的对象，也就是相同的（适用于equals方法）的对象只会存放一个，但是这里实际上是两个对象a,b都被放到了HashSet中，这样HashSet就失去了他本身的意义了。

此时我们把equals方法给加上：

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 publicclassHashTest{ 
 privateinti; 
  
 publicintgetI(){ 
 returni; 
 } 
  
 publicvoidsetI(inti){ 
 this.i=i; 
 } 
  
 <spanstyle="color:#3366FF;"><strong>publicbooleanequals(Objectobject){ 
 if(object==null){ 
 returnfalse; 
 } 
 if(object==this){ 
 returntrue; 
 } 
 if(!(objectinstanceofHashTest)){ 
 returnfalse; 
 } 
 HashTestother=(HashTest)object; 
 if(other.getI()==this.getI()){ 
 returntrue; 
 } 
 returnfalse; 
 }</strong></span> 
  
 publicinthashCode(){ 
 returni%10; 
 } 
  
 publicfinalstaticvoidmain(String[]args){ 
 HashTesta=newHashTest(); 
 HashTestb=newHashTest(); 
 a.setI(1); 
 b.setI(1); 
 Set<HashTest>set=newHashSet<HashTest>(); 
 set.add(a); 
 set.add(b); 
 System.out.println(a.hashCode()==b.hashCode()); 
 System.out.println(a.equals(b)); 
 System.out.println(set); 
 } 
 } 

此时得到的结果就会如下：

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 true 
 true 
 [com.ubs.sae.test.HashTest@1] 

从结果我们可以看出，现在两个对象就完全相等了，HashSet中也只存放了一份对象。

没有重写equals

示例代码

[java]<wbr></wbr>view plaincopy
 //2.<wbr>验证唯一性，存入自定义元素</wbr><wbr><wbr></wbr></wbr> 
 class<wbr>Person{<wbr><wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>private</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr>String<wbr>name;<wbr><wbr></wbr></wbr></wbr></wbr></span></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>private</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr></wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>int</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr>age;<wbr><wbr></wbr></wbr></wbr></span></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>public</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr></wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>static</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr></wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>void</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr>sop(Object<wbr>o){<wbr><wbr></wbr></wbr></wbr></wbr></span></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>System.out.println(o);<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr>}<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>public</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr>Person(String<wbr>name,<wbr></wbr></wbr></wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>int</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr>age){<wbr><wbr></wbr></wbr></wbr></span></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>this</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">.name<wbr>=name;<wbr><wbr></wbr></wbr></wbr></span></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>this</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">.age<wbr>=age;<wbr><wbr></wbr></wbr></wbr></span></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr>}<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>public</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr></wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>void</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr>setName(String<wbr>name){<wbr><wbr></wbr></wbr></wbr></wbr></span></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>this</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">.name<wbr>=name;<wbr><wbr></wbr></wbr></wbr></span></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr>}<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>public</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr>String<wbr>getName(){<wbr><wbr></wbr></wbr></wbr></wbr></span></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>return</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr></wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>this</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">.name;<wbr><wbr></wbr></wbr></span></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr>}<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>public</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr></wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>void</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr>setAge(</wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>int</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr>age){<wbr><wbr></wbr></wbr></wbr></span></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>this</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">.age<wbr>=age;<wbr><wbr></wbr></wbr></wbr></span></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr>}<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>public</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr></wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>int</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr>getAge(){<wbr><wbr></wbr></wbr></wbr></span></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>return</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr></wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>this</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">.age;<wbr><wbr></wbr></wbr></span></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr>}<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>public</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr>String<wbr>toString(){<wbr><wbr></wbr></wbr></wbr></wbr></span></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>return</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr></wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>this</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">.name+</span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:blue; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">"::"</span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">+</span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>this</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">.age;<wbr><wbr></wbr></wbr></span></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr>}<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 }<wbr><wbr></wbr></wbr> 

测试代码：

[java]<wbr></wbr>view plaincopy

classHashSetDemoIII
{
<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">public<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">static<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">void<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">sop(Objecto){
System.out.println(o);
}
<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">public<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">static<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">void<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">main(String[]args){
HashSeths=<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">new<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">HashSet();
hs.add(<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">new<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">Person(<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:blue; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">"a1"<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">,<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(192,0,0); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">11<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">));
hs.add(<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">new<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">Person(<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:blue; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">"a2"<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">,<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(192,0,0); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">12<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">));
hs.add(<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">new<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">Person(<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:blue; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">"a3"<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">,<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(192,0,0); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">13<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">));
hs.add(<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">new<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">Person(<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:blue; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">"a2"<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">,<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(192,0,0); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">12<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">));
Iteratorit=hs.iterator();
<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">while<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">(it.hasNext()){
sop(it.next());
}
}
}

测试结果：

【结论】循环迭代结果：a2::12被打印了两次，说明重复的元素newPerson("a2", 12)被添加到集合中去。没有保证HashSet的唯一性。

{3}. 为Person类重写equals()方法判定两个对象的内容是否一致

[java]<wbr></wbr>view plaincopy
 public<wbr></wbr>boolean<wbr>equals(Object<wbr>obj){<wbr><wbr></wbr></wbr></wbr></wbr> 
 if(!(obj<wbr></wbr>instanceof<wbr>Person)){<wbr><wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>return</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr></wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>false</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">;<wbr><wbr></wbr></wbr></span></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr>}<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr>Personp<wbr>=(Person)obj;<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,130,0); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">//用来查看equals方法是否被调用</span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr><wbr></wbr></wbr></span></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr>sop(<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>this</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">.name<wbr>+</wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:blue; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">".......equals......."</span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">+<wbr>p.name);<wbr><wbr></wbr></wbr></wbr></span></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,130,0); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">//认为名字相同并且年龄一样大的两个对象是一个</span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr><wbr></wbr></wbr></span></wbr></wbr></wbr></wbr> 
 return<wbr></wbr>this.name.equals(p.name)<wbr>&amp;&amp;<wbr></wbr></wbr>this.age<wbr>==<wbr>p.age;<wbr><wbr></wbr></wbr></wbr></wbr> 
 }<wbr><wbr></wbr></wbr> 

测试结果：

【结论】循环迭代结果：a2::12被打印了两次，说明重复的元素newPerson("a2", 12)被添加到集合中去。没有保证HashSet的唯一性。

同时equals没有被调用，说明仅仅重写equals方法没起到作用

【分析】HashSet在存储元素的时候，是先查看两个对象的哈希值是否一样的。

{3}【1】.

如果哈希值是一样，再调用元素对象的equals方法，查看两个对象的内容是否一样。

{1}. 如果equlas比较的值一样，说明两个对象相同，不能添加到HashSet对应的集合中。

{2}. 如果equlas比较的值不一样，说明两个对象不同，可以添加到HashSet对应的集合中

{3}【2】.

【本例分析】这个例子中，由于四个Person类的对象都是new出来的，所以没有重写的hashCode是调用本地方法产生的值，所以一定是四个不相同的hashCode值。hashCode值都不一样，equals方法不起作用。

(3). 重写HashCode方法

为避免内容重复的数据添加到HashSet集合中，就必须重写hashCode()方法。

[1]. hashCode的返回值设置为统一的数值：

示例代码：

[java]<wbr></wbr>view plaincopy
 public<wbr></wbr>int<wbr>hashCode(){<wbr><wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr>System.out.println(<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>this</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">.name<wbr>+</wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:blue; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">"...hashCode"</span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">);<wbr><wbr></wbr></wbr></span></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>return</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr></wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(192,0,0); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">60</span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">;<wbr><wbr></wbr></wbr></span></wbr></wbr></wbr></wbr> 
 }<wbr><wbr></wbr></wbr> 

打印结果：

重复的元素没有被添加进来。

【建议】不要将hashCode的返回值都设置成一样的。因为hashCode的值和内存地址有关，这样设置不科学

[2]. 根据比较的条件重写HashCode方法

[java]<wbr></wbr>view plaincopy
 public<wbr></wbr>int<wbr>hashCode(){<wbr><wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr>sop(<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>this</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">.name<wbr>+</wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:blue; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">"......hashCode"</span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">);<wbr><wbr></wbr></wbr></span></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>return</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr></wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>this</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">.name.hashCode()<wbr>+<wbr></wbr></wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(192,0,0); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">29</span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">*age;<wbr><wbr></wbr></wbr></span></wbr></wbr></wbr></wbr> 
 }<wbr><wbr></wbr></wbr> 

这种做法，同样可以避免HashSet集合中不会存入相同元素。

【两种方式的具体区别和详细过程见个人总结。】

(4). 重写hashCode和equals的时候，常犯的错误

[1]. 子类重写hashCode的时候，将方法名写错，写成hasCode

[2]. 子类重写equals的时候，将参数传错，本来应该是public boolean equals(Object obj){}却写成了public boolean equals(自定义类型自定义类型引用)。这样集合框架的底层不会调用这个重载的方法。

2.HashSet总结

1). HashCode如何保证元素唯一性？

(1). 需要重写的方法

通过重写自定义类的hashCode()和equals( )两个方法来达到元素的唯一性保证。

(2). 方法重写之后，执行的顺序

[1]. 如果元素的hashCode值相同，才会使用equals()方法进行判断。

[2]. 如果元素的hashCode值不同，不会调用equals()方法。

2). 开发中的建议

(1). 自定义对象，一定要重写hashCode和equals两个方法

如果不重写，则默认的本地方法hashCode【OS来产生】会产生值都不一样的hashCode，即使内容重复的元素也会被添加到HashSet中，无法保证元素的唯一性。

【注意】开发中重写这两个方法，方便集合框架的底层调用这些方法。

(2). 建立高效的hashCode会使得hashSet添加元素的过程更为高效。

hashCode的值不同，则调用equals()方法比较的环节便可以省去。

3). HashSet判断和删除元素的依据

示例代码：

[java]<wbr></wbr>view plaincopy
 <wbr></wbr>public<wbr></wbr>class<wbr>HashSetDemoIV<wbr>{<wbr><wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>public</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr></wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>static</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr></wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>void</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr>main(String[]<wbr>args)<wbr>{<wbr><wbr></wbr></wbr></wbr></wbr></wbr></span></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>HashSeths<wbr>=<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>new</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr>HashSet();<wbr><wbr></wbr></wbr></wbr></span></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>hs.add(<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>new</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr>Person(</wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:blue; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">"a1"</span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">,<wbr></wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(192,0,0); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">11</span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">));<wbr><wbr></wbr></wbr></span></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>hs.add(<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>new</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr>Person(</wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:blue; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">"a2"</span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">,<wbr></wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(192,0,0); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">12</span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">));<wbr><wbr></wbr></wbr></span></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>hs.add(<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>new</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr>Person(</wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:blue; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">"a3"</span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">,<wbr></wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(192,0,0); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">13</span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">));<wbr><wbr></wbr></wbr></span></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>System.out.println(<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:blue; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">"hashSet中的元素："</span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">+<wbr>hs);<wbr><wbr></wbr></wbr></wbr></span></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>System.out.println(<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:blue; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">"************************"</span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">);<wbr><wbr></wbr></wbr></span></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>System.out.println(<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:blue; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">"HashSet的<wbr>contains依据："</wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">+<wbr>hs.contains(</wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>new</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr>Person(</wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:blue; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">"a1"</span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">,<wbr></wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(192,0,0); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">11</span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">)));<wbr><wbr></wbr></wbr></span></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>System.out.println(<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:blue; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">"************************"</span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">);<wbr><wbr></wbr></wbr></span></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>System.out.println(<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:blue; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">"HashSet的<wbr>remove依据："</wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">+<wbr>hs.remove(</wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(0,102,153); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><strong>new</strong></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px"><wbr>Person(</wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:blue; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">"a3"</span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">,<wbr></wbr></span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:rgb(192,0,0); border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">13</span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">)));<wbr><wbr></wbr></wbr></span></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>System.out.println(<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:blue; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">"************************"</span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">);<wbr><wbr></wbr></wbr></span></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>System.out.println(<span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; color:blue; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">"hashSet中的元素："</span><span style="word-wrap:normal; word-break:normal; border-bottom-width:medium; border-bottom-style:none; border-bottom-color:initial; border-left-width:medium; border-left-style:none; border-left-color:initial; padding-bottom:0px; margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-left:0px; padding-right:0px; border-top-width:medium; border-top-style:none; border-top-color:initial; border-right-width:medium; border-right-style:none; border-right-color:initial; padding-top:0px">+<wbr>hs);<wbr><wbr></wbr></wbr></wbr></span></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr>}<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 }<wbr><wbr></wbr></wbr> 