Java TreeMap remove()用法及代码示例

java.util.TreeMap.remove()是TreeMap类的内置方法，用于从映射中删除任何特定键的映射。它本质上删除了Map中任何特定键的值。

用法:

Tree_Map.remove(Object key)

参数：该方法采用一个参数键，该键的映射关系将从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。

以下示例程序旨在说明java.util.TreeMap.remove()方法的用法：
示例1:传递现有 key 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}

示例2:传递新 key 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：可以对具有不同数据类型的变化和组合的任何类型的映射执行相同的操作。

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注：本文由纯净天空筛选整理自Chinmoy Lenka大神的英文原创作品 TreeMap remove() Method in Java。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。