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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