In this example we are going to create a multirelease JAR file that provides different implementation for the same class that are used with different JDK versions (8 and 9 in the particular example).
In the source folder there are two projects with similar structure. You can incorporate different strategies for compiling a multirelease JAR file from sources but in this example we are going to use a fairly straigforward one - we are going to compile the two projects and build the multirelease JAR from a combination of the class files in the two projects.
Create a new class ProcessManager in the Project_JDK9 project with the same API as the ProcessManager class in the Project_JDK8 project that lists all operating system processes. Use the utilities provided by the new ProcessHandle class in JDK9.
Use the compile.sh script to compile the projects (each project must be compiled using different JDK version but for this example we compiling both projects with JDK9 compiler - modify the compile.js script accordingly to compile the separate project with JDK8 installation on your workstation):
$ ./compile.sh
Use the command below to create the multirelease JAR file:
$ jar --create --file multirelease.jar -C src/Project_JDK8/target/classes . --release 9 -C src/Project_JDK9/target/classes .
Note: The important bit here is the --release argument that provides the compiled version of the class for the specific JDK release we target.
And we run the JAR with the run.sh script against different JDK8 and JDK9 and you can inspect the difference:
$ ./run.sh