Codeground AI

Java Online Compiler

Write a class with main(), compile, run. JDK is on our side — nothing to install locally.

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Java

About this editor

Write a class with main(), compile, run. JDK is on our side — nothing to install locally.

javac and java run in a sandbox with the same compile-then-run flow as your laptop. Use it for LeetCode-style classes, university OOP assignments, and verifying imports before an interview. Compiler errors and stack traces show in the output panel so you can iterate fast.

Key features

Java runs server-side

javac compiles, then java runs your class in a sandbox — normal compile-run cycle.

One-click Run

Output, stderr, and compiler errors land in the panel below. No local install.

VS Code–like editor

Syntax highlighting, bracket matching, and shortcuts that feel familiar if you use VS Code.

Shareable links

Save with a title and copy the URL — handy for reviews, homework, or interview screens.

No setup

Open the page and start typing. Account optional for basic runs.

Room to grow

Need multiple files? Open a cloud workspace from the top bar.

Getting started

  1. 1
    Write your code

    Type or paste Java in the editor. A starter template is there if you want to run something immediately.

  2. 2
    Press Run

    Check the output panel underneath for results or errors.

  3. 3
    Edit and rerun

    Change a line, run again. Most people loop here until the output looks right.

  4. 4
    Save for a permalink

    Add a title when you save. You get a link you can send to a teammate or drop in a doc.

  5. 5
    Bigger project?

    Cloud workspaces handle multi-file repos and longer sessions. Link is in the top nav.

Common questions

Is this Java compiler free?

Yes. No payment and no account required for a quick run. Sign in if you want saves tied to your profile.

Do I need to install anything?

No. Code runs on Codeground servers in a sandbox. Just open the page.

What Java version runs here?

Modern JDK in a sandbox. Typical interview imports work; Maven multi-module projects need a workspace.

Can I share my code?

Save with a title to get a permalink, or share the playground URL as-is.

Works for interviews?

Yes. Share a ground link, or use interview mode for a live shared editor.

Multiple files?

This page is for single-file snippets. Use a cloud workspace for full projects.

Will my code still be here tomorrow?

Anonymous sessions can reset. Save with a title (and sign in) for a stable link.

Why use this instead of installing locally?

Good for quick tests, learning, and sharing a snippet. For large offline work, a local IDE still wins.

Is this an online Java IDE or playground?

A browser playground with syntax highlighting and one-click Run — run Java online without a full local install. Cloud workspaces cover multi-file projects.

Is there a free Java playground?

Yes. Compile and run Java online for free—no JDK download and no account for a quick run.

Is this a Java online IDE?

A browser Java IDE with editor and Run—enough for single-class snippets. Maven multi-module work needs a workspace.

Can I run Java online without installing the JDK?

Yes. javac and java run on Codeground servers. Open the page in any browser—no local JDK setup.