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  • 2018-08-29  10:16:28        
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    Java.util.HashMap.remove()是HashMap类的内置方法,用于从map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:

    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.HashMap.remove()方法的工作原理

    HashMap.remove()程序1:传递现有密钥时。

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

    输出:

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

    HashMap.remove()程序2:传递新密钥时。

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

    输出:

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

    注意:对于具有不同数据类型的变体和组合的任何类型的映射,都可以执行相同的操作。

     
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