ConcurrentHashMap containsValue() Method in Java

The java.util.concurrent.ConcurrentHashMap.containsValue() method is an in-built function in Java which accepts a value and returns true if one or more keys are mapped to the specified value. This method traverses the entire hashtable. Thus it is a much slower function than containsKey() method.

Syntax:

chm.containsValue(Object val_element)

Parameters: The method accepts a single parameter val_element of object type which is to be checked for whether it is mapped to any key in the map or not.

Return Value: The method returns true if the specified val_element is mapped to any key in this map and false otherwise.

Exception: The function throws NullPointerException when the specified value_element is null.

Below programs illustrate the use of java.util.concurrent.ConcurrentHashMap.containsValue() method :

Program 1: This program involves mapping Integer Values to String Keys.

/* Java Program to demonstrate containsValue() 
   method of ConcurrentHashMap */
  
import java.util.concurrent.*; 
class ConcurrentHashMapDemo { 
    public static void main(String[] args) 
    { 
        ConcurrentHashMap<String, Integer> chm =  
                    new ConcurrentHashMap<String, Integer>(); 
        chm.put("Geeks", 120); 
        chm.put("for", 11); 
        chm.put("GeeksforGeeks", 15); 
        chm.put("Gfg", 50); 
        chm.put("GFG", 25); 
  
        // Check whether a key is mapped to 100 
        if (chm.containsValue(100)) { 
            System.out.println("100 is mapped."); 
        } 
        else { 
            System.out.println("100 is not mapped."); 
        } 
  
        // Check whether a key is mapped to 120 
        if (chm.containsValue(120)) { 
            System.out.println("120 is mapped."); 
        } 
        else { 
            System.out.println("120 is not mapped."); 
        } 
    } 
} 

Output:

100 is not mapped.
120 is mapped.

Program 2: This program involves mapping String Values to Integer Keys.

/* Java Program to demonstrate containsValue() 
   method of ConcurrentHashMap */
  
import java.util.concurrent.*; 
class ConcurrentHashMapDemo { 
    public static void main(String[] args) 
    { 
        ConcurrentHashMap<Integer, String> chm =  
                 new ConcurrentHashMap<Integer, String>(); 
        chm.put(100, "Geeks"); 
        chm.put(101, "for"); 
        chm.put(102, "Geeks"); 
        chm.put(103, "Gfg"); 
        chm.put(104, "GFG"); 
  
        // Check whether a key is mapped to Geeks 
        if (chm.containsValue("Geeks")) { 
            System.out.println("Geeks is mapped."); 
        } 
        else { 
            System.out.println("Geeks is not mapped."); 
        } 
  
        // Check whether a key is mapped to GfG 
        if (chm.containsValue("GfG")) { 
            System.out.println("GfG is mapped."); 
        } 
        else { 
            System.out.println("GfG is not mapped."); 
        } 
    } 
} 

Output:

Geeks is mapped.
GfG is not mapped.

Reference : https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ConcurrentHashMap.html#containsValue()

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