Java WeakHashMap get() 方法

java.util.WeakHashMap.get() 方法返回指定键映射到的值，如果map不包含该键所对应的值，则返回 null。

返回值 null 并不一定表示该map不包含该键的所对应的值；因为map也可能显式地将键对应的值设为为 null。

语法

public V get(Object key) 

这里，V是容器维护的值的类型。

参数

返回值

返回指定键映射到的值，如果此map不包含该键所对应的值，则返回 null。

异常

示例:

在下面的示例中，java.util.WeakHashMap.get() 方法返回给定键中映射到的值map。

import java.util.*;

public class MyClass {
  public static void main(String[] args) {
    //创建weakhashmap
    WeakHashMap<Integer, String> MyMap = new WeakHashMap<Integer, String>();

    //填充map
    MyMap.put(101, "John");
    MyMap.put(102, "Marry");
    MyMap.put(103, "Kim");
    MyMap.put(104, "Jo");

    //打印指定键的映射值
    System.out.println("101 is mapped to: " + MyMap.get(101));
    System.out.println("102 is mapped to: " + MyMap.get(102));
    System.out.println("103 is mapped to: " + MyMap.get(103));
    System.out.println("104 is mapped to: " + MyMap.get(104));  
  }
} 

上述代码的输出将是:

101 is mapped to: John
102 is mapped to: Marry
103 is mapped to: Kim
104 is mapped to: Jo