Java TreeMap remove()方法

java.util.TreeMap.remove()是TreeMap类的一个内置方法，用于从地图中删除任何特定键的映射。它基本上是删除地图中任何特定键的值。

语法

Tree_Map.remove( _Object key_ )

参数： 该方法需要一个参数 key ，其映射要从Map中移除。

返回值： 如果键存在，该方法将返回之前映射到指定键上的值，否则该方法将返回NULL。

下面的程序说明了java.util.TreeMap.remove()方法的工作。

程序1： 当传递一个现有的键时。

// 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);
 
        // Displaying 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： 当传递一个新的密钥时。

// 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);
 
        // Displaying 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： 同样的操作可以通过不同数据类型的变化和组合对任何类型的Mapping进行操作。