Java 21.0

Online Java Compiler & Editor

Name: myCompiler Java
Author: myCompiler

myCompiler is a free online Java compiler, editor and code runner that lets you write, run, and share Java code directly in your browser. It works as your Java playground, sandbox, fiddle, cloud compiler, and online REPL. No downloads, no installation needed. Just open the editor and start coding with syntax highlighting, autocomplete, and instant output.

Start coding in Java How it works

27+ languages Used by 1M+ developers Free forever

main.java

import java.util.*;

public class Main {
    public static void main(String[] args) {
        List<String> names = Arrays.asList(
            "Alice", "Bob", "Charlie");
        names.stream()
            .map(String::toUpperCase)
            .forEach(System.out::println);
    }
}

Output

ALICE BOB CHARLIE

How to run Java code online

Three steps to go from idea to running Java code in this online playground. No account required.

Write your code

Open the Java editor and start writing. The smart editor gives you syntax highlighting, autocomplete, and error detection as you type.

Click Run

Hit the Run button or press +Enter to run your Java code on secure, sandboxed cloud servers.

See results

Output appears instantly in the integrated terminal. Errors and exceptions show up with clear, helpful messages.

Everything you need to code in Java

A complete online Java IDE and coding playground in your browser. Write, run, and share code without any setup.

Zero setup required

Start coding in seconds with this browser-based Java interpreter. No downloads, no installations, no environment configuration. Open your browser, go to myCompiler, and start writing Java code immediately.

Works on any device with a web browser. Desktop, laptop, tablet, phone, Chromebook. There is nothing to install and nothing to configure.

Feature-rich code editor

Write Java with a professional-grade code editor built into your browser. Syntax highlighting colors your code for readability, making keywords, strings, and functions easy to distinguish at a glance.

Intelligent autocomplete suggests methods and properties as you type, and real-time error detection catches mistakes before you run your code.

Multi-file projects

Create and manage multiple files in a single project. Use the file sidebar to organize your code into modules, then import them across files just like in a desktop IDE.

Build modular applications with proper project structure. Each file is editable, and you can switch between them instantly.

Run code instantly

Click the Run button or press +Enter to execute your Java code instantly. This online code runner displays output immediately in the integrated terminal panel. Your code runs on secure, sandboxed cloud servers and results appear in seconds.

Error messages and tracebacks are displayed clearly, making it easy to find and fix issues. The terminal supports ANSI colors for rich output formatting.

Ready to try it? Write and run your first Java program in seconds.

Open Java editor

Java on myCompiler

myCompiler runs Java 21.0, always up to date with the latest stable release. You get a full browser-based IDE with syntax highlighting, intelligent code completion, multi-file project support, a built-in terminal for real-time output, and standard input (stdin) for interactive programs. Write, compile, run, and debug Java code on any device. Desktop, laptop, tablet, phone, Chromebook. Zero downloads, zero configuration, and no sign-up required. Save your programs with a unique URL and share them with anyone. You can also embed a working Java editor on your own website.

Use this online Java playground as a quick code executor for testing snippets, a coding sandbox for learning, or a cloud compiler for coding interview preparation. The editor includes dark mode for comfortable coding, keyboard shortcuts for faster workflows, and clear error messages with line numbers so you can debug quickly. Students use it for homework and practice. Teachers use it to share working examples. Developers use it to prototype ideas. myCompiler is beginner-friendly, fast, and completely free. It works in any modern web browser.

Start coding in Java

Java code examples

Common Java patterns you can try in the online compiler. Each example is ready to run.

Hello World in Java

main.java

public class Main {
    public static void main(String[] args) {
        System.out.println("Hello, World!");
    }
}

Variables and Data Types in Java

main.java

public class Main {
    public static void main(String[] args) {
        String name = "Alice";
        int age = 30;
        System.out.println(name + " is " + age);
    }
}

If-Else Conditionals in Java

main.java

public class Main {
    public static void main(String[] args) {
        int x = 10;
        if (x > 0) System.out.println("Positive");
        else if (x == 0) System.out.println("Zero");
        else System.out.println("Negative");
    }
}

For and While Loops in Java

main.java

public class Main {
    public static void main(String[] args) {
        for (int i = 0; i < 5; i++)
            System.out.println("Count: " + i);

        String[] fruits = {"apple", "banana", "cherry"};
        for (String fruit : fruits)
            System.out.println(fruit);
    }
}

Functions in Java

main.java

public class Main {
    static String greet(String name) {
        return "Hello, " + name + "!";
    }
    static String greet(String name, String greeting) {
        return greeting + ", " + name + "!";
    }
    public static void main(String[] args) {
        System.out.println(greet("Alice"));
        System.out.println(greet("Bob", "Hi"));
    }
}

Arrays and Collections in Java

main.java

import java.util.*;

public class Main {
    public static void main(String[] args) {
        List<String> fruits = new ArrayList<>(Arrays.asList("apple", "banana"));
        fruits.add("cherry");
        System.out.println(fruits.get(1));

        Map<String, Integer> person = new HashMap<>();
        person.put("age", 30);
        System.out.println("Age: " + person.get("age"));
    }
}

Classes and Objects in Java

main.java

public class Main {
    static class Dog {
        String name, breed;
        Dog(String name, String breed) {
            this.name = name; this.breed = breed;
        }
        String bark() { return name + " says Woof!"; }
    }
    public static void main(String[] args) {
        Dog dog = new Dog("Rex", "Labrador");
        System.out.println(dog.bark());
    }
}

Error Handling in Java

main.java

public class Main {
    public static void main(String[] args) {
        try {
            int result = Integer.parseInt("not a number");
        } catch (NumberFormatException e) {
            System.out.println("Error: " + e.getMessage());
        } finally {
            System.out.println("Done");
        }
    }
}

File I/O in Java

main.java

import java.io.*;

public class Main {
    public static void main(String[] args) throws Exception {
        try (PrintWriter pw = new PrintWriter("output.txt")) {
            pw.println("Hello, File!");
        }
        try (BufferedReader br = new BufferedReader(new FileReader("output.txt"))) {
            System.out.println(br.readLine());
        }
    }
}

Streams API in Java

main.java

import java.util.*;
import java.util.stream.*;

public class Main {
    public static void main(String[] args) {
        List<Integer> nums = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
        int sum = nums.stream()
            .filter(n -> n % 2 == 0)
            .mapToInt(Integer::intValue)
            .sum();
        System.out.println("Sum of evens: " + sum);
    }
}

Try these examples in the editor

How to take input in Java online

myCompiler supports standard input (stdin) for Java programs. Use Java's standard input functions to read user input. Enter your input data in the stdin panel before running your program.

This works for both single-line and multi-line input. You can read strings and convert to numbers using the language's built-in I/O functions.

Try it yourself

main.java stdin supported

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String name = sc.nextLine();
        int age = Integer.parseInt(sc.nextLine());

        System.out.println("Hello " + name + "!");
        System.out.println("You'll be " + (age + 1) + " next year.");
    }
}

stdin

Alice
25

Output

Hello Alice!
You'll be 26 next year.

No setup, no sign-up. Start writing Java code right now.

Start coding now

Getting started with Java online

You can start writing and running Java code right now without installing anything. Type your code, and click Run. This free Java code runner executes your program instantly and displays the output in the terminal panel below the editor. Open the Java online editor, type your code, and click Run.

If you're new to Java, use this online Java playground to start with the basics like variables, data types, conditionals, and loops. The code examples above cover all the fundamentals you need to get started. Each example can be copied into the sandbox and run immediately. No setup, no configuration.

As you progress, try creating multi-file projects, using libraries, and sharing your programs with others via URL. Sign up for a free account to save your work and build a personal library of programs. myCompiler works as a full online Java IDE right in your browser.

Who uses myCompiler

Whether you're learning to code, preparing for interviews, or prototyping ideas, myCompiler is built for you.

Students & Learners

Practice exercises, complete homework assignments, and experiment with code without installing anything on school or personal computers.

Teachers & Educators

Share code examples with students via unique URLs. Embed the compiler in course materials so students can run examples directly in the browser.

Interview Candidates

Practice coding interview problems, test algorithms, and verify solutions quickly during preparation for technical interviews.

Professional Developers

Quickly prototype ideas, test code snippets, or try out a library without setting up a local environment. Great for quick experiments.

Content Creators & Bloggers

Embed interactive examples in blog posts, tutorials, and documentation so readers can run code without leaving the page.

Teams & Collaborators

Share code snippets with colleagues via URLs. Others can view, run, and fork your code to build on your work.

myCompiler vs. local IDE

Why use an online Java compiler instead of installing one locally?

Feature	myCompiler	Local IDE
Setup time	Instant	Minutes to hours
Installation	None required	Java + IDE required
Device support	Any browser	Desktop only
Sharing code	One-click URL	Manual (file, git, etc.)
Languages	27+ in one place	One at a time
Cost	Free forever	Free to $$$
Works on Chromebook	Yes	Limited

What is Java?

Java is a class-based, object-oriented programming language designed by James Gosling at Sun Microsystems and first released in 1995. Java's revolutionary "write once, run anywhere" principle means compiled Java bytecode runs on any device with a Java Virtual Machine (JVM), regardless of the underlying operating system or hardware.

Java is one of the most widely deployed programming languages in the world. The Android mobile platform runs on Java, billions of enterprise applications run on the JVM, and the language has been a staple of university computer science curricula for decades. Modern Java versions (Java 17, 21) have introduced records, sealed classes, pattern matching, and virtual threads that modernize the language significantly.

What is Java used for?

Java is used for enterprise applications with Spring Boot and Jakarta EE, Android app development, web services and REST APIs, big data processing with Apache Hadoop and Spark, financial systems at banks and trading firms, and cloud applications. The JVM also hosts other languages like Kotlin, Scala, and Clojure, making the Java ecosystem exceptionally broad.

Java for beginners

Java is a popular first language in university CS programs because it teaches strong object-oriented programming concepts including encapsulation, inheritance, and polymorphism. Its strict type system catches many errors at compile time, and the verbose syntax, while sometimes criticized, forces beginners to be explicit about what they are doing. Use myCompiler's online Java compiler to write and run Java programs instantly without installing the JDK.

Java vs other languages

Compared to Python, Java is more verbose but faster, more structured, and better for large team codebases where strict typing prevents bugs. Compared to C#, Java and C# are very similar, C# is Microsoft's Java alternative with more modern language features in recent years. Compared to Kotlin, Java is more verbose but has a longer track record and larger legacy codebase ecosystem. Kotlin is fully interoperable with Java and the preferred language for new Android development.

Why use an online Java compiler?

An online Java compiler, also called a Java sandbox or Java playground, lets you compile and run Java programs directly in your browser without installing the JDK or an IDE like Eclipse or IntelliJ. This is perfect for practicing object-oriented design patterns, preparing for Java-based coding interviews, learning core Java APIs, and testing algorithms without setting up a development environment.

myCompiler's online Java IDE supports modern Java features including records, text blocks, sealed classes, and the Stream API. The full Java standard library is available, including java.util, java.io, and java.util.stream. Save and share programs, add stdin input for interview practice, all free.

Why is Java so popular?

Java has been among the top three programming languages on TIOBE for over two decades. Its platform independence, strong typing, mature ecosystem, and enterprise adoption are the pillars of its longevity. The Android ecosystem alone accounts for billions of Java-running devices. Despite newer JVM languages like Kotlin and Scala, Java itself continues to evolve with major features and remains the default choice for enterprise Java shops, financial institutions, and large-scale distributed systems.

Java career opportunities

Java skills are in high demand for software engineer, backend developer, Android developer, enterprise architect, and big data engineer roles. Java developers are among the most sought after globally, with strong demand at banks, insurance companies, enterprise software firms, and tech giants. Java expertise combined with Spring Boot is one of the most common tech stacks in enterprise job postings.

Try Java online Free · No sign-up needed

Keyboard shortcuts

Code faster with these keyboard shortcuts in the myCompiler editor.

Run code

+ Enter

Save program

+ S

Toggle comment

+ /

Indent line

Tab

Unindent line

Shift + Tab

Undo

+ Z

Select next occurrence

+ D

Find & replace

+ H

Embed the Java compiler on your website

Add an interactive Java compiler to your website, blog, or learning platform. Readers can write and run Java code directly on your page without leaving it.

Perfect for technical tutorials, coding courses, documentation, and educational content. Save a program on myCompiler and use the embed link to add it to any webpage.

Embedded Java compiler, editor and code runner

HTML

<iframe
src="https://www.mycompiler.io
    /embed/java"
width="100%"
height="400"
frameborder="0">
</iframe>

Why developers choose myCompiler

A full-featured online IDE for Java and 27+ other programming languages.

27+ Languages

Python, JavaScript, Java, C++, Rust, Go, TypeScript, C#, and many more. All compilers and interpreters in one place. Switch languages instantly.

Dark & Light Mode

Switch between light and dark themes with one click. Code comfortably in any lighting condition, day or night.

Mobile Friendly

Fully responsive editor optimized for phones, tablets, and Chromebooks. Code on any device with a web browser. No app download needed.

Save & Share Code

Save programs to your account, share via unique URLs, and let others view, fork, and run your code. Great for collaboration and code reviews.

Tags & Organization

Organize your saved programs with tags and find them quickly with search and filters. Build a personal library of code snippets and solutions.

No Account Required

Start writing and running code immediately. No sign-up, no email, no credit card. Create a free account later only if you want to save your work.

Explore more programming languages

myCompiler supports 27+ languages. Switch between them anytime. All free, all in one place.

View all 27+ languages

Frequently asked questions

Common questions about using the online Java compiler, playground, and code runner.

Yes! myCompiler is completely free for all supported languages including Java. There are no subscriptions, no premium tiers, and no hidden costs. Every feature is available at no charge.

myCompiler keeps its Java environment up to date. You can see the exact version on the language details section of this page. We regularly update all language runtimes to their latest stable versions.

myCompiler runs Java on a recent version of the JDK. You can see the exact version in the language details section. The environment supports modern Java features including records, pattern matching, and text blocks.

Simply open the Java editor, write or paste your code, and click the Run button. Your code will be executed on our servers and the output will appear in the terminal panel within seconds.

Yes. Click Save to store your program. You will receive a unique URL that you can share with anyone. Recipients can view, fork, and run your code.

Yes. myCompiler supports multi-file projects. You can create, rename, and delete files in the sidebar. This lets you organize your Java code just like in a local IDE.

Yes. All code runs in isolated containers on our servers. Each execution gets its own sandboxed environment that is destroyed after completion. Your code cannot affect other users or our infrastructure.

Yes. myCompiler has a responsive design optimized for phones and tablets. You can write and run Java code on the go. The mobile interface uses tabs for switching between the editor, output, and file panels.

Yes. Click the Input tab in the bottom panel, type or paste your input data, then click Run. Your program will read from the input you provided.

Execution is fast. Code runs on our optimized cloud infrastructure and output typically appears within seconds. Execution time depends on the complexity of your program.

Yes. myCompiler provides an embed feature. You can copy an iframe snippet and paste it into your website, blog, or documentation. Visitors can edit and run code directly on your page.

myCompiler supports common editor shortcuts including Run (Ctrl/Cmd+Enter), Save (Ctrl/Cmd+S), Find (Ctrl/Cmd+F), and more. See the keyboard shortcuts section on this page for the full list.

No. myCompiler requires an internet connection because code is compiled and executed on our cloud servers. The editor itself loads in your browser, but running code requires connectivity.

myCompiler offers a fast, free, zero-setup environment with a modern code editor, multi-file support, dark mode, and instant sharing. It is ideal for learning, prototyping, interviews, and sharing code examples.

Yes. myCompiler is great for practicing algorithms and coding problems. You can write Java code, provide custom input, and test your solutions instantly. Save your work and come back to it anytime.

Use print statements or console output to trace your program's behavior. myCompiler shows all standard output and error messages in the terminal panel. Error messages include line numbers to help you locate issues.

Ready to write Java code?

Open the free Java playground and start coding immediately. No downloads, no account required.

Start coding in Java

Free · No sign-up required · Java 21.0