Java 8 Stream Collectors groupingBy Example

In this article we are going to see about Java 8 Stream Collectors groupingBy with example program.

StreamGroupBy.java

package com.javatutorialcorner.java8;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.function.Function;
import java.util.stream.Collectors;

public class StreamGroupBy {

 public static void main(String[] args) {
  List batsmanRanking = new ArrayList<>();
  batsmanRanking.add("Virat Kohli");
  batsmanRanking.add("AB de Villiers");
  batsmanRanking.add("David Warner");
  batsmanRanking.add("Joe Root");
  batsmanRanking.add("Kane Williamson");
  batsmanRanking.add("Quinton de Kock");
  batsmanRanking.add("AB de Villiers");
  batsmanRanking.add("Faf du Plessis");
  batsmanRanking.add("Virat Kohli");
  batsmanRanking.add("Babar Azam");
  batsmanRanking.add("Quinton de Kock");
  batsmanRanking.add("Martin Guptill");
  batsmanRanking.add("Shikhar Dhawan");
  batsmanRanking.add("AB de Villiers");
  batsmanRanking.add("Virat Kohli");
  batsmanRanking.add("Faf du Plessis");

  System.out.println("Java 8 Group by a List and display the total count.");

  Map result = batsmanRanking.stream()
    .collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));

  System.out.println(result);
 }

}

Output

Java 8 Group by a List and display the total count.
{Faf du Plessis=2, Virat Kohli=3, Martin Guptill=1, Babar Azam=1, Quinton de Kock=2, Kane Williamson=1, AB de Villiers=3, Joe Root=1, Shikhar Dhawan=1, David Warner=1}