Don't think of it as alternative to java, think of it as an alternative to writing the critical path of bigger java code in opencl/assembler/fortran. With this

Don't think of it as alternative to java, think of it as an alternative to writing the critical path of bigger java code in opencl/assembler/fortran. With this you can write the critical method in subset of java, test it using standard java tooling and then run it on gpu. All your tools will work because it's a subset of java - so you can use the same code formatter, static analysis tools, build scripts, continuous integration, IDE highlighting and completion. You can use IDE refactoring over the whole codebase instead of doing it in 2 phases on 2 different languages (or more often doing the performance-sensitive parts by hand). That's a big difference, much better than maintaining codebase in 2 languages one of which usually isn't supported by your tools.