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    TreeMap的java.util.TreeMap.put()方法用于将映射插入到映射中。这意味着我们可以将特定键及其映射的值插入到特定映射中。如果传递现有密钥,则先前的值将被新值替换。如果传递了一对新对,那么该对将作为整体插入。

    句法:

    Tree_Map.put(key, value)

    参数:该方法有两个参数,都是TreeMap的Object类型。

    • key:这是指需要插入Map进行映射的关键元素。
    • value:这是指上面的键映射到的值。

    返回值:如果传递现有密钥,则返回先前的值。如果传递了一对新对,则返回NULL。

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

    程序1:传递现有密钥时。

    // Java code to illustrate the put() 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);
      
            // Inserting existing key along with new value
            String returned_value = (String)tree_map.put(20, "All");
      
            // 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, 20=All, 25=Welcomes, 30=You}

    程序2:传递新密钥时。

    // Java code to illustrate the put() 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);
     
            // Inserting existing key along with new value
            String returned_value = (String)tree_map.put(50, "All");
     
            // 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, 50=All}

    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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