Java TreeMap containsValue()方法及示例

在Java中，TreeMap类的containsValue()方法用于检查一个特定的值是否被TreeMap中的任何键所映射。它以值为参数，如果该值被地图中的任何一个键映射，则返回True。

--> java.util Package 
    --> TreeMap class
        --> containsValue() Method

语法

Tree_Map.containsValue( _Object Value_ )

参数： 对象类型的值，指的是其映射应该被地图内的任何键检查的值。( 只有一个参数)

返回类型： 一个布尔值，如果该值的映射被检测到则为真，否则为假。

注意：在java中，当返回布尔值时，只返回true false，而不是0和1，因为这是不允许的，所以在编译时将产生错误。

例1： 将字符串值映射到整数键。

// Java Program to Illustrate containsValue() 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 and 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);
 
        // Checking for custom value in map
        // using containsValue() method
 
        // Say for the Value 'Geeks'
        System.out.println(
            "Is the value 'Geeks' present? "
            + tree_map.containsValue("Geeks"));
 
        // Checking for the Value 'World'
        System.out.println(
            "Is the value 'World' present? "
            + tree_map.containsValue("World"));
    }
}

输出

Initial Mappings are: {10=Geeks, 15=4, 20=Geeks, 25=Welcomes, 30=You}
Is the value 'Geeks' present? true
Is the value 'World' present? false

例2： 将整数值映射到字符串键。

// Java Program  to illustrate containsValue() 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);
        hastree_map_map.put("You", 30);
 
        // Printing the elements of TreeMap
        System.out.println("Initial Mappings are: "
                           + tree_map);
 
        // Checking for the Value '10'
        // using containsValue() method
        System.out.println("Is the value '10' present? "
                           + tree_map.containsValue(10));
 
        // Checking for the Value '30'
        System.out.println("Is the value '30' present? "
                           + tree_map.containsValue(30));
 
        // Checking for the Value '40'
        System.out.println("Is the value '40' present? "
                           + tree_map.containsValue(40));
    }
}

输出

Java中的TreeMap containsValue方法及示例