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  • 2018-09-18  22:36:17        
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    java.util.TreeMap.remove()是TreeMap类的内置方法,用于从map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。

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

    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<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}

    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<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: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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