Where does my Java code run?

On a sandboxed third-party execution service, not on induwara.lk's servers. Your code is sent to an isolated compiler environment, run there, and the result is returned. Our server only forwards the request (with strict rate limits and size caps) — it never executes your code, so there's no way for a program to reach our systems.

Is the Java compiler free to use, and do I need an account?

Yes, it's completely free and there's no signup. Just write your code and press Run. It's meant as a quick, zero-setup way to compile and test code from any device, including a phone.

How should I structure my Java code here?

Use a non-public class named Main with `public static void main(String[] args)` — exactly as the default snippet shows. (The class is non-public because the sandbox compiles to a fixed filename; a public class would error with 'should be declared in a file named Main.java'.) Add your logic inside main, or extra methods/classes in the same file.

Is this good for A-Level / university Java practice?

Yes — it's a zero-install way to practise Java from any device. Write a class, run it, see the output. Ideal for testing loops, arrays, OOP concepts, and exam-style exercises without setting up a JDK locally.

Which compiler / version is used?

It runs OpenJDK (a recent Java release) on the sandboxed compiler, so modern language features work. Put your code in a public class with a standard static main method.

Are there limits on run time or code size?

Each run has a 30-second limit and a 50 KB code-size cap, and there are per-IP and overall rate limits so the shared compiler stays fast for everyone. For big projects use a local toolchain; this is built for snippets, exercises, and quick tests.

Can I read interactive input (stdin) while it runs?

Interactive input isn't wired into this editor yet — programs run start-to-finish and their output is shown. For exercises that need input, set the values directly as variables in your code. Everything printed to standard output appears in the output panel.

Developer · Runs in your browser

Online Java Compiler — write, compile & run Java

Compile and run Java instantly online, free and with no signup. Your code runs on a sandboxed compiler — not on our servers — so it's safe, isolated, and works from any device.

By Induwara Ashinsana— Executive Director, Ryzera TechnologiesUpdated May 28, 2026

Java · runs on a sandboxed server

Loading editor…

Output

Press Run to execute. Output appears here.

How it works

Java needs the JDK to compile .java source into bytecode and a JVM to run it — which a browser can't do. So this compiler does it server-side: write a class with a main method, press Run, and the compiled program's output comes back.

When you press Run, your Java code is sent to a sandboxed execution service that compiles and runs it in an isolated environment, then returns the output. It does notrun on induwara.lk's servers — our site only proxies the request, so your code can never touch our systems, files, or other users. Languages like Javaneed a real compiler/runtime, which isn't practical in a browser, so this is the safe way to offer them.

The proxy is strictly bounded: a 30-second execution limit, a 50 KB code cap, and per-IP plus global rate limits that protect the shared compiler. There's no signup and nothing to install — write code, hit Run, read the output.

Frequently asked questions

Sources & references

Compilation + execution happen on Wandbox's isolated servers; induwara.lk only proxies the request with rate limits and caps.

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Found a bug or want another language added?

Email me at [email protected].