Hi,
To get started, you need to use Java 8 (OpenJDK is fine) for the main development, or Java 11 (again, OpenJDK works well) for development on branch `java-10-gradle`. Use Gradle to build and test JPF:
./gradlew test
will build and test it.
On Java 8, all tests should pass. On Java 11, there are a few tests that still fail; these features, which are not fully supported on Java 11 yet, are a good starting point for a proposal on Java 11 bytecode support. You can start to look at why one of these tests fails, and perhaps find a smaller feature/test that is (part of) the root cause of the failure. That will be the first step towards a plan for fixing it.
One unit test may fail because of multiple reasons, and it may require multiple fixes (for different features in bytecode that don't fully work yet for Java 11).
Conversely, one feature (such as automated toString calls on objects inside a print statement on Java 11) may cause multiple tests to fail, and fixing it will fix several tests at once.