Playground

Write code. Hit run.

Java, Python, Node — no account, no setup, nothing to install. Two of the three never leave your machine.

Python & Node run in your tabJava compiles in a sandboxNo network, no filesystem, hard timeout

runs in a sandboxOpenJDK 21 · isolated sandbox

public class Main {
    public static void main(String[] args) {
        System.out.println("Hello from Java " + System.getProperty("java.version"));

        int[] nums = {5, 2, 9, 1, 7};
        java.util.Arrays.sort(nums);
        System.out.println(java.util.Arrays.toString(nums));
    }
}

Tab indents · Shift+Tab dedents · Esc then Tab leaves the editor

Output

Output appears here. Press ⌘/Ctrl + ↵ to run.

Curious how the sandbox holds?

Running a stranger's Java on the same box that serves this site is the most dangerous thing here. Every run is a transient systemd unit with no network, /home invisible, a read-only root, a throwaway uid, capped memory and CPU, and one run at a time behind a queue — and none of the request ever becomes a command argument.

Read the architecture