Java ConcurrentHashMap contains()用法及代码示例

Java.util.ConcurrentHashMap的contains()方法用于检查某些键是否映射到该表中的指定值。它是执行特定任务的传统方法。该操作类似于ConcurrentHashMap的containsValue()方法。

用法:

ConcurrentHashMap.contains(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。

下面的程序用于说明ConcurrentHashMap.containsValue()方法的用法：

示例1:将字符串值映射到整数键。

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

输出：

Initial Mappings are: {20=Geeks, 25=Welcomes, 10=Geeks, 30=You, 15=4}
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 contains() method 
  
import java.util.*; 
import java.util.concurrent.*; 
  
public class ConcurrentHashMapDemo { 
    public static void main(String[] args) 
    { 
  
        // Creating an empty ConcurrentHashMap 
        ConcurrentHashMap<String, Integer> 
            hash_map = new ConcurrentHashMap<String, 
                                             Integer>(); 
  
        // Mapping int values to string keys 
        hash_map.put("Geeks", 10); 
        hash_map.put("4", 15); 
        hash_map.put("Geeks", 20); 
        hash_map.put("Welcomes", 25); 
        hash_map.put("You", 30); 
  
        // Displaying the ConcurrentHashMap 
        System.out.println("Initial Mappings are: "
                           + hash_map); 
  
        // Checking for the Value 'Geeks' 
        System.out.println("Is the value 'Geeks' present? "
                           + hash_map.contains(25)); 
  
        // Checking for the Value 'World' 
        System.out.println("Is the value 'World' present? "
                           + hash_map.contains(35)); 
    } 
}

输出：

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

相关用法

注：本文由纯净天空筛选整理自Chinmoy Lenka大神的英文原创作品 ConcurrentHashMap contains() method in Java with Examples。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。