Java中的java.util.TreeMap.clear()方法用于清除和删除指定TreeMap中的所有元素或映射。

句法:

Tree_Map.clear()

参数:该方法不接受任何参数。

返回值:该方法不返回任何值。

下面的程序用于说明java.util.TreeMap.clear()的工作方法

程序1:将字符串值映射到整数键。

// Java code to illustrate the clear() 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);
  
        // Clearing the tree map using clear()
        tree_map.clear();
  
        // Displaying the final TreeMap
        System.out.println("Finally the map looks like: " + tree_map);
    }
}

输出:

Initial Mappings are: {10=Geeks, 15=4, 20=Geeks, 25=Welcomes, 30=You}
Finally the map looks like this: {}

程序2:将 整数值映射到字符串键。

// Java code to illustrate the clear() method
import java.util.*;
 
public class Tree_Map_Demo {
    public static void main(String[] args)
    {
 
        // Creating an empty TreeMap
        TreeMap<String, Integer> tree_map = new TreeMap<String, Integer>(); 
 
        // Mapping int values to string keys
        tree_map.put("Geeks", 10);
        tree_map.put("4", 15);
        tree_map.put("Geeks", 20);
        tree_map.put("Welcomes", 25);
        tree_map.put("You", 30);
 
        // Displaying the TreeMap
        System.out.println("Initial Mappings are: " + tree_map);
 
        // Clearing the tree map using clear()
        tree_map.clear();
 
        // Displaying the final TreeMap
        System.out.println("Finally the map looks like: " + tree_map);
    }
}

输出:

Initial Mappings are: {4=15, Geeks=20, Welcomes=25, You=30}
Finally the map looks like: {}

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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