Java WeakHashMap remove()方法

java.util.WeakHashMap.remove()是WeakHashMap类的一个内置方法，用于从地图中删除任何特定键的映射。它基本上是删除地图中任何特定键的值。

语法

Weak_Hash_Map.remove(Object key)

参数： 该方法需要一个参数key，其映射要从Map中移除。

返回值： 如果键存在，该方法返回先前映射到指定键的值，否则该方法返回NULL。

下面的程序说明了java.util.WeakHashMap.remove()方法的工作原理：

程序1： 当传递一个现有的键时。

// Java code to illustrate the remove() method
import java.util.*;
  
public class Weak_Hash_Map_Demo {
    public static void main(String[] args)
    {
  
        // Creating an empty WeakHashMap
        Map<Integer, String> weak_hash = new 
                       WeakHashMap<Integer, String>();
    
        // Mapping string values to int keys
        weak_hash.put(10, "Geeks");
        weak_hash.put(15, "4");
        weak_hash.put(20, "Geeks");
        weak_hash.put(25, "Welcomes");
        weak_hash.put(30, "You");
  
        // Displaying the WeakHashMap
        System.out.println("Initial Mappings are: " + 
                                           weak_hash);
  
        // Removing the existing key mapping
        String returned_value = 
                         (String)weak_hash.remove(20);
  
        // Verifying the returned value
        System.out.println("Returned value is: " + 
                                      returned_value);
  
        // Displayin the new map
        System.out.println("New map is: " + weak_hash);
    }
}

输出：

Initial Mappings are: {30=You, 15=4, 10=Geeks, 25=Welcomes, 20=Geeks}
Returned value is: Geeks
New map is: {30=You, 15=4, 10=Geeks, 25=Welcomes}

程序2： 当传递一个新的密钥时。

// Java code to illustrate the remove() method
import java.util.*;
  
public class Weak_Hash_Map_Demo {
    public static void main(String[] args)
    {
  
        // Creating an empty WeakHashMap
        Map<Integer, String> weak_hash = 
                   new WeakHashMap<Integer, String>();
  
        // Mapping string values to int keys
        weak_hash.put(10, "Geeks");
        weak_hash.put(15, "4");
        weak_hash.put(20, "Geeks");
        weak_hash.put(25, "Welcomes");
        weak_hash.put(30, "You");
  
        // Displaying the WeakHashMap
        System.out.println("Initial Mappings are: " + 
                                          weak_hash);
  
        // Removing the new key mapping
        String returned_value = 
                        (String)weak_hash.remove(50);
  
        // Verifying the returned value
        System.out.println("Returned value is: " + 
                                    returned_value);
  
        // Displayin the new map
        System.out.println("New map is: "+weak_hash);
    }
}

输出：

Initial Mappings are: {30=You, 15=4, 10=Geeks, 25=Welcomes, 20=Geeks}
Returned value is: null
New map is: {30=You, 15=4, 10=Geeks, 25=Welcomes, 20=Geeks}

注意： 同样的操作可以通过不同数据类型的变化和组合对任何类型的Mapping进行操作。