How to implement custom collector using Java Stream?

In this tutorial, we will learn how to implement custom collector using java 8 stream.

4 Methods

To create a custom collector, we need to implement the four main methods defined by the Collector interface: supplier, accumulator, combiner, and finisher. The collector interface was provided by Java 8 under the part of the newly introduced Java Stream API.

Why we need to implement Custom collector in Java ?

Implementing a custom collector in Java becomes necessary when the built-in collectors provided by the Java Stream API do not fulfill the specific requirements of your data processing task.

Steps to Create Custom Collector :

As we know to create custom collector we need to implement the interface with the below-mentioned methods.

Supplier
Accumulator
Combiner
Finish

Okay Lets Start to write the code and try to understand How to build custom collector.

package com.demo.main;

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collector;
import java.util.stream.Collectors;

public class TestCustomCollector {

    public static void…