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    TreeMap类的java.util.TreeMap.size()方法用于获取映射的大小,该大小是指Map中键值对或映射的数量。

    句法:

    Tree_Map.size()

    参数:该方法不接受任何参数。

    返回值:该方法返回映射的大小,这也表示映射中存在的键值对的数量。

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

    程序1:将字符串值映射到整数键。

    // Java code to illustrate the size() 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);
      
            // Displaying the size of the map
            System.out.println("The size of the map is " + tree_map.size());
        }
    }
    

    输出:

    Initial Mappings are: {10=Geeks, 15=4, 20=Geeks, 25=Welcomes, 30=You}
    The size of the map is 5

    程序2:将整数值映射到字符串键。

    // Java code to illustrate the size() 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);
     
            // Displaying the size of the map
            System.out.println("The size of the map is " + tree_map.size());
        }
    }
    

    输出:

    Initial Mappings are: {4=15, Geeks=20, Welcomes=25, You=30}
    The size of the map is 4

    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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