Java中的 TreeMap remove() 方法

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：
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 tree_map = 
                   new TreeMap();
  
        // 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 tree_map = 
                    new TreeMap();
  
        // 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：可以对任何类型的映射执行相同的操作，这些映射具有不同数据类型的变化和组合。