Java中TreeMap的remove()方法: TreeMap.remove()

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

java.util.TreeMap.remove()是TreeMap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:

Tree_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.TreeMap.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 Tree_Map_Demo { 
    public static void main(String[] args) 
    { 
  
        // Creating an empty TreeMap 
        TreeMap<Integer, String> tree_map =  
                   new TreeMap<Integer, String>(); 
  
        // Mapping string values to int keys 
        tree_map.put(10, "Geeks"); 
        tree_map.put(15, "4"); 
        tree_map.put(20, "Geeks"); 
        tree_map.put(25, "Welcomes"); 
        tree_map.put(30, "You"); 
  
        // Displaying the TreeMap 
        System.out.println("Initial Mappings are: " 
                                         + tree_map); 
  
        // Removing the existing key mapping 
        String returned_value = (String)tree_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: " + tree_map); 
    } 
} 

输出:

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

程序2:传递新密钥时。

// Java code to illustrate the remove() method 
import java.util.*; 
  
public class Tree_Map_Demo { 
    public static void main(String[] args) 
    { 
  
        // Creating an empty TreeMap 
        TreeMap<Integer, String> tree_map =  
                    new TreeMap<Integer, String>(); 
  
        // Mapping string values to int keys 
        tree_map.put(10, "Geeks"); 
        tree_map.put(15, "4"); 
        tree_map.put(20, "Geeks"); 
        tree_map.put(25, "Welcomes"); 
        tree_map.put(30, "You"); 
  
        // Displaying the TreeMap 
        System.out.println("Initial Mappings are: " 
                                          + tree_map); 
  
        // Removing the new key mapping 
        // Note : 50 is not present and so null 
        // should be returned (nothing to remove) 
        String returned_value = (String)tree_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: " + tree_map); 
    } 
} 

输出:

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

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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