Java Compilers

Overview

The Java compiler javac is available on the CSF but should not be used on the login node. You need to load one of the available openjdk modules.

Version 1.8.0 of the OpenJDK is installed in the CSF. You do not need to load any module for using this. However, the javac compiler is not installed with it.
You can use any of the the following openjdk modules if you need Java compiler:

Restrictions on use

None.

Set up procedure

Version 1.8.0 is the default JRE version available if no modulefile is loaded. The following modulefiles are also available if a specific version is required:

module load tools/openjdk/25.0.1               # JDK 25
module load tools/openjdk/23.0.2               # JDK 23
module load tools/openjdk/22.0.2               # JDK 22
module load tools/openjdk/20.0.2               # JDK 20
module load tools/openjdk/17.0.2               # JDK 17
module load tools/openjdk/11.0.2               # JDK 11

Running the application

As a quick test, create a file named HelloWorld.java using a text editor on the CSF (e.g. using gedit) which contains the following:

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello World");
    }
}

Then compile the code using:

javac HelloWorld.java

Now run the code using:

java HelloWorld

# It should print:
Hello World

Due to recent excessive memory usage on the login node, all processes running on that node are now restricted in their memory usage. The javac compiler will not execute on the login node, reporting a memory limit error:

Error occurred during initialization of VM
Could not reserve enough space for object heap
Could not create the Java virtual machine.

You should start an interactive session using srun to launch a shell on a compute node that has more memory. You can then run javac as normal.

Interactive Usage

Request an interactive session using:

On the login node:
srun -p interactive -n 1 -t 0-1 --pty bash
  #
  # Wait for a new prompt to appear (e.g., [username@node770])
  #
javac ...

Running Compiled Java Code

Please read the Java application launcher notes for how to run java code in the batch system with the correct number of threads.

Further info

Updates