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ConcurrentHashMap contains() method in Java with Examples

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  • Last Updated : 30 Oct, 2018
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The contains() method of Java.util.ConcurrentHashMap is used to check whether if some key maps into the specified value in this table. It is a legacy method of performing a particular task. The operation is similar to containsValue() Method of ConcurrentHashMap.

Syntax:

ConcurrentHashMap.contains(Object Value)

Parameters: The method takes just one parameter Value of Object type and refers to the value whose mapping is supposed to be checked by any key inside the map.

Return Value: The method returns boolean true if the mapping of the value is detected else false.

Below programs are used to illustrate the working of ConcurrentHashMap.containsValue() Method:

Program 1: Mapping String Values to Integer Keys.




// 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"));
    }
}

Output:

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

Program 2: Mapping Integer Values to String Keys.




// 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));
    }
}

Output:

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

Note: The same operation can be performed with any type of Mappings with variation and combination of different data types.


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