Java TreeMap values()方法及示例

在Java中，TreeMap类的values()方法存在于java.util包中，用于从地图的值中创建一个集合。它基本上返回TreeMap中数值的一个集合视图。

--> java.util package
    --> TreeMap class
        --> values() Method  

语法

Tree_Map.values()

返回类型： 一个包含地图所有值的集合视图。

现在我们将提出不同的集合来说明values()方法，具体如下。

1. 将字符串值映射到整数键
2. 将整数值映射到字符串键上

例子1： 将字符串值映射到整数键上

// Java Program to illustrate values() Method
// of TreeMap class
 
// Importing required classes
import java.util.*;
 
// Main class
public class GFG {
 
    // Main driver method
    public static void main(String[] args)
    {
        // Creating an empty TreeMap by
        // declaring object of integer, string pairs
        TreeMap<Integer, String> tree_map
            = new TreeMap<Integer, String>();
 
        // Mapping string values to int keys
        // using put() method
        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");
 
        // Printing the elements of TreeMap
        System.out.println("Initial Mappings are: "
                           + tree_map);
 
        // Getting the set view of values
        // using values() method
        System.out.println("The collection is: "
                           + tree_map.values());
    }
}

输出

Initial Mappings are: {10=Geeks, 15=4, 20=Geeks, 25=Welcomes, 30=You}
The collection is: [Geeks, 4, Geeks, Welcomes, You]

例2： 将整数值映射到字符串键。

// Java Program to Illustrate values() method
// of TreeMap class
 
// Importing required classes
import java.util.*;
 
// Main class
public class GFG {
 
    // Main driver method
    public static void main(String[] args)
    {
        // Creating an empty TreeMap by
        // declaring object of string, integer pairs
        TreeMap<String, Integer> tree_map
            = new TreeMap<String, Integer>();
 
        // Mapping int values to string keys
        // using put() method
        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);
 
        // Printing the elements of TreeMap
        System.out.println("Initial Mappings are: "
                           + tree_map);
 
        // Getting the set view of values
        // using values() method
        System.out.println("The collection is: "
                           + tree_map.values());
    }
}

输出

Initial Mappings are: {4=15, Geeks=20, Welcomes=25, You=30}
The collection is: [15, 20, 25, 30]

注意： 同样的操作可以通过不同数据类型的变化和组合对任何类型的Mapping进行操作。