Tag: group by

java8 March 15, 2020 by mkyong 4 comments

Java 8 – Find duplicate elements in a Stream

This article shows you three algorithms to find duplicate elements in a Stream. Set.add() Collectors.groupingBy Collections.frequency At the end of the article, we use the JMH benchmark to test which one is the fastest algorithm. 1. Filter & Set.add() The Set.add() returns false if the element was already in the set; let see the benchmark […]

java8 April 7, 2016 by mkyong 36 comments

Java 8 – Stream Collectors groupingBy examples

In this article, we will show you how to use Java 8 Stream Collectors to group by, count, sum and sort a List. 1. Group By, Count and Sort 1.1 Group by a List and display the total count of it. Java8Example1.java package com.mkyong.java8; import java.util.Arrays; import java.util.List; import java.util.Map; import java.util.function.Function; import java.util.stream.Collectors; public […]