Java

Summary

Item	Value
API name	java
source OCI image	eclipse-temurin:21-jdk-alpine
per-job resource ceiling	2 vCPU, 1024 MiB

The vCPU and RAM ceiling exists to prevent abuse; libkrun memory is elastic and the host only pays for what the guest touches.

Warmup

None: the official image already ships everything needed.

How the code is executed

The main file (the first in files) is compiled with javac and the Main class is run with java Main. Therefore:

• the class with main must be named Main;
• the file must be named Main.java.

With bare code in /api/v1/execute, the guest writes Main.java on its own. A compilation error returns exception: "Compilation failed", with the javac output in stderr. Everything runs in a directory under /tmp (tmpfs), in a fresh VM destroyed at the end of the job, with no network.

Building the image

rc image build --stack java

Example

curl -s http://127.0.0.1:8080/api/v1/run \
  -H 'Content-Type: application/json' \
  -d '{
    "language": "java",
    "files": [
      {"name": "Main.java", "content": "public class Main {\n    public static void main(String[] args) {\n        System.out.println(6 * 7);\n    }\n}\n"}
    ]
  }'

Expected stdout: 42.