Run Java 23 online

What's in Java 23

• JEP 467: Markdown syntax accepted in Javadoc comments.
• JEP 474: ZGC uses its generational mode by default — less memory, same latency.
• Second previews of primitive patterns and flexible constructor bodies.

What you get in Java 23

Clicking "Run now" opens the playground with this exact code and a matching test case — passes on first Run.

import java.util.Scanner;
public class Solution {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    System.out.println(n * 2);
  }
}

How ls-judge runs Java 23

Every submission is compiled and executed inside its own Firecracker microVM — the same isolation primitive AWS Lambda uses. No shared container, no shared kernel with other users' code. The Java 23toolchain shipped with the microVM is the real thing (not a browser-side emulation): syscalls behave the way they do in production, and the compile / runtime behaviour matches what you would see on your own machine with that version installed.

Feed stdin from the Tests panel, watch verdicts stream per test case over a WebSocket. Free to use, no sign-up, works from any browser.