# distinct() method

Paul Tomoiu

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Examples,

Streams

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Published 2023-06-10

This tutorial explains how we can use distinct() method for Streams in Java.

distinct() method creates a stream without duplicates.

Please take a look at the following example and read carefully the comments. The code is self-explanatory.

This example is created from a simple Spring Boot application created with Spring Initializr. I am using Maven, Java 17, Spring Boot 3.1.0.

From the base application downloaded from Spring Initializr, I updated the main class as below:

DemoApplication.java
package com.example.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;

import java.util.Arrays;
import java.util.Collection;
import java.util.Comparator;
import java.util.List;
import java.util.concurrent.ExecutionException;

@SpringBootApplication
public class DemoApplication {

	public static void main(String[] args) throws InterruptedException, ExecutionException {

		ApplicationContext appContext = SpringApplication.run(DemoApplication.class, args);

		List<List<String>> wordsList = Arrays.asList(
				Arrays.asList("Laptop", "BMW", "Laptop"),
				Arrays.asList("John", "Dan Brown"),
				Arrays.asList("computer", "project"));

		wordsList.stream()
				// Stream<List<String>> will be converted to Stream<String>
				.flatMap(Collection::stream)
				// the elements are ordered in ASC mode
				.sorted()
				// the duplicates are removed
				.distinct()
				.forEach(p -> System.out.println(p));

		System.out.println("---------------------------");

	}
}

When I run this code I receive:

BMW
Dan Brown
John
Laptop
computer
project
---------------------------

Process finished with exit code 0

When we are working with Streams, we can have:

INTERMEDIATE operations: filter, map, limit, sorted, peak, distinct, skip, flatMap
TERMINAL operations: forEach, count, sum, min, collect, reduce, anyMatch, noneMatch, allMatch