java HashMap:散列映射表

最新推荐文章于 2024-11-14 00:52:57 发布

原创最新推荐文章于 2024-11-14 00:52:57 发布 · 702 阅读

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CC 4.0 BY-SA版权

文章标签：

#hashmap #java #string #basic #c# #class

本文通过一个具体的Java程序示例，展示了如何使用HashMap进行键值对的存储与操作，包括添加、删除元素及获取集合等常见操作。

/*HashMap:散列映射表
* 使用同一键值调用两次put方法，第二个值将取代第一个值
* remove方法用于移除包含给定键的元素*/
import java.util.*;
public class MapTest {
    public static void main(String[] args)
    {
    Map<String,Language> book=new HashMap<String,Language>();
    book.put("first", new Language("java"));
    book.put("second",new Language("c++"));
    book.put("third", new Language("c#"));
    book.put("fouth", new Language("c"));
    System.out.println(book);
    book.remove("first");
    book.put("fifty", new Language("basic"));
    System.out.println(book.get("fouth"));
    /*获取键集*/
    Set<String> keys=book.keySet();
    for(String key:keys)
    {
      System.out.println(key);
    }
    /*获取值集合*/
    Collection<Language> values=book.values();
    for(Language value:values)
    {
      System.out.println(value);
    }
    /*获取键/值对的集合*/
    //Set<Map.Entry<String, Language>> keyAndValues=book.entrySet();
    for(Map.Entry<String, Language> entry:book.entrySet())
    {
      String key=entry.getKey();
      Language value=entry.getValue();
      System.out.println("key="+key+",value="+value);
    }
    }
}
class Language
{
private String name;
private int number;
public Language(String n)
{
  name=n;
}
public String toString()
{
  return "[name="+name+",number="+number+"]";
}
}

程序输出结果：

{first=[name=java,number=0], fouth=[name=c,number=0], third=[name=c#,number=0], second=[name=c++,number=0]}
[name=c,number=0]
fifty
fouth
third
second
[name=basic,number=0]
[name=c,number=0]
[name=c#,number=0]
[name=c++,number=0]
key=fifty,value=[name=basic,number=0]
key=fouth,value=[name=c,number=0]
key=third,value=[name=c#,number=0]
key=second,value=[name=c++,number=0]