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    Java.util.IdentityHashMap.remove() 是IdentityHashMap类的内置方法,用于从地图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:如果该键存在,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() 方法的工作原理

    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<Integer, String> Identity_hash = new 
                           IdentityHashMap<Integer, String>();
      
            // 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<Integer, String> Identity_hash = 
                       new IdentityHashMap<Integer, String>();
    
            // 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}

     
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