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  • 2018-09-18  22:16:56        
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    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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