Java ConcurrentHashMap forEach() Method

The forEach() method of ConcurrentHashMap class performs the given action for each key, value pair.

Syntax

public void forEach(long parallelismThreshold, BiConsumer<? super K,? super V> action)

public <U> void forEach(long parallelismThreshold, BiFunction<? super K,? super V,? extends U> transformer, Consumer<? super U> action)

Parameter

parallelismThreshold - the (estimated) number of elements needed for this operation to be executed in parallel

action - the action

transformer - a function which return transformation.

Returns

true if the value was replaced

Throws

NullPointerException.

Example 1

import java.util.concurrent.*; 

import java.util.*; 
  
public class  ConcurrentHashMapforeachExample1 { 
  
    public static void main(String[] args) 
    { 
          // crete a HashMap and add some values 
        HashMap<String, Integer> mapcon 
            = new HashMap<>(); 
        mapcon.put("k1", 100); 
        mapcon.put("k2", 200); 
        mapcon.put("k3", 300); 
        mapcon.put("k4", 400); 
        System.out.println("HashMap values :\n " + mapcon.toString());  
        //replace the value of key k1 to 1000
        mapcon.replace("k1" , 1000);
        System.out.println("New HashMap after remove :\n "+ mapcon.toString()); //print statement
        mapcon.forEach( (k, v) -> System.out.printf("    k: %s, v: %s%n", k, v)); //foreach function
    } 
} 

Test it Now

Output:

New HashMap after remove :
 {k1=1000, k2=200, k3=300, k4=400}
    k: k1, v: 1000
    k: k2, v: 200
    k: k3, v: 300
    k: k4, v: 400

Example 2

import java.util.*;
import java.util.concurrent.ConcurrentHashMap;

public class ConcurrentHashMapforeachExample2  {
   public static void main(String args[]) {
      
     ConcurrentHashMap<String , String>  mymap = new ConcurrentHashMap<String ,String>(); 

     ConcurrentHashMap<Integer , Integer>  mymap2 = new ConcurrentHashMap<Integer , Integer>(); 
     
      mymap2.put(1, 101);
      mymap2.put(2, 102);
      mymap2.put(3, 103);
      System.out.println(" mymap2 :" +mymap2.toString());
      mymap.put("AA", "Java");
      mymap.put("BB", "angular");
      mymap.put("CC", "JavaScript");
      System.out.println(" mymap :" +mymap.toString());
      System.out.println("comparing mymap and mymap2 :" +mymap.equals(mymap2));
      mymap.forEach( (k, v) -> System.out.printf("    k: %s, v: %s%n", k, v));
   }    
}

Test it Now

Output:

mymap2 :{1=101, 2=102, 3=103}
 mymap :{AA=Java, BB=angular, CC=JavaScript}
comparing mymap and mymap2 :false
    k: AA, v: Java
    k: BB, v: angular
    k: CC, v: JavaScript

Next TopicJava ConcurrentHashMap

← prev next →