JAVA-HashMap的应用例子

import java.util.*;
class HashMapDemo2
{
<wbr>public static void main(String[] args)<br><wbr>{<br><wbr><wbr>HashMap&lt;Student, String&gt; hm = new HashMap&lt;Student, String&gt;();<br><wbr><wbr><br><wbr><wbr>hm.put(new Student("张三", 20), "北京");<br><wbr><wbr>hm.put(new Student("李四", 21), "西安");<br><wbr><wbr>hm.put(new Student("王五", 15), "重庆");<br><wbr><wbr>hm.put(new Student("赵六", 26), "成都");<br><wbr><wbr>hm.put(new Student("小七", 12), "绵阳");<br><wbr><wbr>hm.put(new Student("小七", 12), "绵阳"); //未覆盖hashCode方法和equals方法时，能够存入相同的元素.<br><wbr><wbr><br><wbr><wbr>Set &lt;Map.Entry&lt;Student, String&gt;&gt; s = hm.entrySet();<br><wbr><wbr>for (Iterator&lt;Map.Entry&lt;Student, String&gt;&gt; it = s.iterator(); it.hasNext(); )<br><wbr><wbr>{<br><wbr><wbr><wbr>Map.Entry&lt;Student, String&gt; me = it.next();<br><wbr><wbr><wbr>Student stu = me.getKey();<br><wbr><wbr><wbr>String addr = me.getValue();<br><wbr><wbr><wbr>System.out.println(stu.getName() + ".." + stu.getAge() + ".." + addr);<br><wbr><wbr>}<wbr><wbr><br><wbr>}<br> }</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></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

class Student
{
<wbr>private String name;<br><wbr>private int age;<br><wbr>Student(String name, int age)<br><wbr>{<br><wbr><wbr>this.name = name;<br><wbr><wbr>this.age<wbr> = age;<br><wbr>}</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr>public String getName()<br><wbr>{<br><wbr><wbr>return name;<br><wbr>}<br><wbr>public int getAge()<br><wbr>{<br><wbr><wbr>return age;<br><wbr>}</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr>public int hashCode()<wbr> //注意，判断HashSet、HashMap集合的唯一性，覆盖hashCode和equals方法，而TreeMap、TreeMap排序实现comparable或comparator接口.<br><wbr>{<br><wbr><wbr>return name.hashCode() + age*29;<br><wbr>}</wbr></wbr></wbr></wbr></wbr></wbr>

<wbr>public boolean equals(Object obj)<br><wbr>{<br><wbr><wbr>if (!(obj instanceof Student))<br><wbr><wbr><wbr>return false;<br><wbr><wbr>Student student = (Student)obj;<br><wbr><wbr>return this.name.equals(student.name) &amp;&amp; this.age == student.age;<wbr><wbr><br><wbr>}</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr>public String toString()<br><wbr>{<br><wbr><wbr>return name + ".." + age;<br><wbr>}<br> }<br></wbr></wbr></wbr></wbr></wbr>