Java Function apply()

🎓 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 Function apply() method in Java programming and how to use it with an example.

1. Function apply() Method Overview

Definition:

The Function.apply() method is a method in the Function interface, used to compute a result using the provided argument and return it. A Function is a part of the java.util.function package, which is a functional interface representing a function that accepts an argument and produces a result.

Syntax:

R apply(T t)

Parameters:

- t: The function argument.

Key Points:

- The Function.apply() method takes one argument and produces a result.

- It is a functional interface and thus can be used as the assignment target for a lambda expression or method reference.

- The primary use case is to transform data from one form to another.

2. Function apply() Method Example

import java.util.function.Function;

public class FunctionApplyExample {
    public static void main(String[] args) {
        // Define a Function to convert an integer to its string representation
        Function<Integer, String> intToString = num -> Integer.toString(num);

        // Define a Function to double an integer
        Function<Integer, Integer> doubleNumber = num -> num * 2;

        // Apply the functions
        String result1 = intToString.apply(5);
        int result2 = doubleNumber.apply(7);

        System.out.println("Result of intToString: " + result1);
        System.out.println("Result of doubleNumber: " + result2);
    }
}

Output:

Result of intToString: 5
Result of doubleNumber: 14

Explanation:

In the example provided, we first define a Function that converts an integer to its string representation. Another Function is defined to double the integer. Using the apply() method, we then compute and print the results. The first function transforms the number 5 into its string form, while the second function doubles the number 7 to produce 14.

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