Java Set contains() example

🎓 Top 15 Udemy Courses (80-90% Discount): My Udemy Courses - Ramesh Fadatare — All my Udemy courses are real-time and project oriented courses.

▶️ Subscribe to My YouTube Channel (178K+ subscribers): Java Guides on YouTube

▶️ For AI, ChatGPT, Web, Tech, and Generative AI, subscribe to another channel: Ramesh Fadatare on YouTube

In this guide, you will learn about the Set contains() method in Java programming and how to use it with an example.

1. Set contains() Method Overview

Definition:

The contains() method of the Java Set interface returns true if the set contains the specified element.

Syntax:

boolean exists = set.contains(Object o);

Parameters:

- Object o: The element whose presence in this set is to be tested.

Key Points:

- The method returns true if this set contains the specified element.

- This method uses the equals method of the elements to check for equality.

- If the set contains the specified element, it returns true, otherwise, it returns false.

- The method throws a ClassCastException if the type of the specified element is incompatible with this set (optional).

- It also throws a NullPointerException if the specified element is null and this set does not support null elements (optional).

2. Set contains() Method Example

import java.util.HashSet;
import java.util.Set;

public class SetContainsExample {
    public static void main(String[] args) {
        Set<String> fruits = new HashSet<>();

        // Adding elements to the set
        fruits.add("Apple");
        fruits.add("Banana");
        fruits.add("Cherry");

        // Checking if set contains specific elements
        System.out.println("Does the set contain 'Apple'? : " + fruits.contains("Apple"));  // true
        System.out.println("Does the set contain 'Grape'? : " + fruits.contains("Grape"));  // false

        // Using contains() with a null value
        fruits.add(null);  // Assuming the set implementation allows null
        System.out.println("Does the set contain null? : " + fruits.contains(null));  // true
    }
}

Output:

Does the set contain 'Apple'? : true
Does the set contain 'Grape'? : false
Does the set contain null? : true

Explanation:

In this example:

1. We create a HashSet of fruits.

2. We add three fruits: "Apple", "Banana", and "Cherry" to the set.

3. We then check for the presence of "Apple" and "Grape" using the contains() method. As expected, "Apple" exists, while "Grape" does not.

4. We then demonstrate how the contains() method works with null values (assuming the set implementation supports null values).

The contains() method is essential to determine the presence of an element in a set without having to traverse the entire set manually.

Related Java Set interface methods

Java Set add() example
Java Set contains() example
Java Set isEmpty() example
Java Set remove() example
Java Set size() example

My Top and Bestseller Udemy Courses. The sale is going on with a 70 - 80% discount. The discount coupon has been added to each course below:

Build REST APIs with Spring Boot 4, Spring Security 7, and JWT

🆕 High-Demand 80–90% OFF

[NEW] Learn Apache Maven with IntelliJ IDEA and Java 25

🆕 High-Demand 80–90% OFF

ChatGPT + Generative AI + Prompt Engineering for Beginners

🚀 Trending Now 80–90% OFF

Spring 7 and Spring Boot 4 for Beginners (Includes 8 Projects)

🔥 Bestseller 80–90% OFF
Available in Udemy for Business

Building Real-Time REST APIs with Spring Boot - Blog App

🔥 Bestseller 80–90% OFF
Available in Udemy for Business

Building Microservices with Spring Boot and Spring Cloud

🌟 Top Rated 80–90% OFF
Available in Udemy for Business

Java Full-Stack Developer Course with Spring Boot and React JS

🔥 Bestseller 80–90% OFF
Available in Udemy for Business

Build 5 Spring Boot Projects with Java: Line-by-Line Coding

🌟 Top Rated 80–90% OFF

Testing Spring Boot Application with JUnit and Mockito

🔥 Bestseller 80–90% OFF
Available in Udemy for Business

Spring Boot Thymeleaf Real-Time Web Application - Blog App

🔥 Bestseller 80–90% OFF
Available in Udemy for Business

Master Spring Data JPA with Hibernate

🔥 Bestseller 80–90% OFF
Available in Udemy for Business

Spring Boot + Apache Kafka Course - The Practical Guide

🎓 Student Favorite 80–90% OFF
Available in Udemy for Business

Java Testing: Mastering JUnit 5 Framework

🆕 New 80–90% OFF

Reactive Programming in Java: Spring WebFlux and Testing

🌟 Top Rated 80–90% OFF

Spring Boot + RabbitMQ Course - The Practical Guide

🌟 Top Rated 80–90% OFF
Available in Udemy for Business

Functional Programming in Java (Includes Java Collections)

🎓 Student Favorite 80–90% OFF

ChatGPT for Java Developers: Boost Your Productivity with AI

🚀 Trending Now 80–90% OFF