I was programming Java Shared Classes Caching on z/OS, and tried using Eclipse IDE on Linux to edit the source. I had several problems with this.

The import files are in a .jmod file, not the .jar files I was expecting.

Compile on z/OS

To compile the Java source on z/OS I needed to add the .jmod file to the classpath.

cp="-cp /usr/lpp/java/J21.0_64/jmods/openj9.sharedclasses.jmod" 
/usr/lpp/java/J8.0_64/J21.0_64/bin/javac $cp m4.java 

With this I could use

...
import com.ibm.oti.shared.*; 
...

When I used the source in the Eclipse IDE, it could not find the imports.

Wrong version of Java

I had installed Java openj9-21 on Linux, but it did not have the openj9.sharedclasses.jmod file.

I downloaded the Semeru code from here.

Often Java is installed in /usr/java/…. files. I installed the new version into one of my personal directories.

The file ibm-semeru-open-jdk_x64_linux_21.0.6_7_openj9-0.49.0.tar.gz was downloaded to my Downloads directory.

You can untar it in place – or unzip it to a different location using the -C …. option

tar -xvf ibm-semeru-open-jdk_x64_linux_21.0.6_7_openj9-0.49.0.tar.gz 

This created a directory jdk-21.0.6+7 and created the files below it.

You can update the “sudo update-alternatives…” command by

sudo update-alternatives –list java
sudo update-alternatives –install /usr/bin/javac javac /home/colinpaice/Downloads/jdk-21.0.6+7/bin/javac
sudo update-alternatives –install /usr/bin/java java /home/colinpaice/Downloads/jdk-21.0.6+7/bin/java 1
sudo update-alternatives –install /usr/bin/jar jar /home/colinpaice/Downloads/jdk-21.0.6+7/bin/jar 1

Which defines which symlinks to define for the javac, java and jar commands.

You also need to update your Java_Home environment variable.

There’s more

I had to configure Eclipse to use this new level of Java. Window-> Preferences-> Installed JREs, and use the location of the directory /home/colinpaice/Downloads/jdk-21.0.6+7.