Java中, IdentityHashMap remove() 的方法

作者: Arvin Chen 分类: Java 来源: Break易站(www.breakyizhan.com)

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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