Java中的IdentityHashMap remove()方法

Java.util.IdentityHashMap.remove() 是 IdentityHashMap 类的内置方法，用于从映射中删除任何特定键的映射。它基本上删除了 Map 中任何特定键的值。

句法：

Identity_Hash_Map.remove(Object key)

参数：该方法采用一个参数键，其映射将从 Map 中删除。

返回值：如果键存在，则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.IdentityHashMap.remove() 方法的工作：
程序 1：传递现有密钥时。

// Java code to illustrate the remove() method
import java.util.*;
  
public class Identity_Hash_Map_Demo {
    public static void main(String[] args)
    {
  
        // Creating an empty IdentityHashMap
        Map Identity_hash = new 
                       IdentityHashMap();
    
        // Mapping string values to int keys
        Identity_hash.put(10, "Geeks");
        Identity_hash.put(15, "4");
        Identity_hash.put(20, "Geeks");
        Identity_hash.put(25, "Welcomes");
        Identity_hash.put(30, "You");
  
        // Displaying the IdentityHashMap
        System.out.println("Initial Mappings are: " + 
                                           Identity_hash);
  
        // Removing the existing key mapping
        String returned_value = 
                         (String)Identity_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: " + Identity_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：传递新密钥时。

// Java code to illustrate the remove() method
import java.util.*;
  
public class Identity_Hash_Map_Demo {
    public static void main(String[] args)
    {
  
        // Creating an empty IdentityHashMap
        Map Identity_hash = 
                   new IdentityHashMap();
  
        // Mapping string values to int keys
        Identity_hash.put(10, "Geeks");
        Identity_hash.put(15, "4");
        Identity_hash.put(20, "Geeks");
        Identity_hash.put(25, "Welcomes");
        Identity_hash.put(30, "You");
  
        // Displaying the IdentityHashMap
        System.out.println("Initial Mappings are: " + 
                                          Identity_hash);
  
        // Removing the new key mapping
        String returned_value = 
                        (String)Identity_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: "+Identity_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：可以对任何类型的映射执行相同的操作，这些映射具有不同数据类型的变化和组合。