Java WeakHashMap containsValue()用法及代码示例

java.util.WeakHashMap.containsValue()方法用于检查特定值是否由WeakHashMap中的单个或多个键映射。它使用Value作为参数，如果该值由映射中的任何键映射，则返回True。

用法:

Weak_Hash_Map.containsValue(Object Value)

参数：该方法仅使用一个Object类型的参数Value，表示应该由映射内的任何键检查其映射的值。

返回值：如果检测到值的映射，则该方法返回布尔值true，否则返回false。

以下示例程序旨在说明java.util.WeakHashMap.containsValue()方法：

示例1:将字符串值映射到整数键。

// Java code to illustrate the containsValue() method 
import java.util.*; 
  
public class Weak_Hash_Map_Demo { 
    public static void main(String[] args) 
    { 
  
        // Creating an empty WeakHashMap 
        Map<Integer, String> weak_hash = new WeakHashMap<Integer, String>(); 
  
        // Mapping string values to int keys 
        weak_hash.put(10, "Geeks"); 
        weak_hash.put(15, "4"); 
        weak_hash.put(20, "Geeks"); 
        weak_hash.put(25, "Welcomes"); 
        weak_hash.put(30, "You"); 
  
        // Displaying the WeakHashMap 
        System.out.println("Initial Mappings are: " + weak_hash); 
  
        // Checking for the Value 'Geeks' 
        System.out.println("Is the value 'Geeks' present? " +  
                                     weak_hash.containsValue("Geeks")); 
  
        // Checking for the Value 'World' 
        System.out.println("Is the value 'World' present? " +  
                                      weak_hash.containsValue("World")); 
    } 
}

输出：

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

示例2:将整数值映射到字符串键。

// Java code to illustrate the containsValue() method 
import java.util.*; 
  
public class Weak_Hash_Map_Demo { 
    public static void main(String[] args) 
    { 
  
        // Creating an empty WeakHashMap 
        Map<String, Integer> weak_hash = new WeakHashMap<String, Integer>(); 
  
        // Mapping int values to string keys 
        weak_hash.put("Geeks", 10); 
        weak_hash.put("4", 15); 
        weak_hash.put("Geeks", 20); 
        weak_hash.put("Welcomes", 25); 
        weak_hash.put("You", 30); 
  
        // Displaying the WeakHashMap 
        System.out.println("Initial Mappings are: " + weak_hash); 
  
        // Checking for the Value '10' 
        System.out.println("Is the value '10' present? " + 
                                    weak_hash.containsValue(10)); 
  
        // Checking for the Value '30' 
        System.out.println("Is the value '30' present? " +  
                                    weak_hash.containsValue(30)); 
  
        // Checking for the Value '40' 
        System.out.println("Is the value '40' present? " + 
                                    weak_hash.containsValue(40)); 
    } 
}

输出：

Initial Mappings are: {Welcomes=25, 4=15, You=30, Geeks=20}
Is the value '10' present? false
Is the value '30' present? true
Is the value '40' present? false

注意：可以对具有不同数据类型的变化和组合的任何类型的映射执行相同的操作。

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注：本文由纯净天空筛选整理自Chinmoy Lenka大神的英文原创作品 WeakHashMap containsValue() Method in Java。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。