bf VS Maker

I also used ProGuardCORE in a Brainfuck compiler that generates bytecode/classfiles in a jar: https://github.com/mrjameshamilton/bf/blob/master/src/main/kotlin/eu/jameshamilton/bf/backend/jvm/JvmCodeGenerator.kt

Something else that could make your code generation for your JVM language easier: ProGuardCORE (https://github.com/Guardsquare/proguard-core). It can be used to read, generate and analyse Java bytecode.

Some examples for code generation: ProGuard where the project originated (https://github.com/Guardsquare/proguard), Brainf*ck compiler (https://github.com/mrjameshamilton/bf), Lox compiler (https://github.com/mrjameshamilton/klox)

Disclaimer: I work at Guardsquare on ProGuardCORE so may be biased ;)

If you want an alternative to ASM, try Cojen/Maker, which is designed to be much easier to use than any of the other class writing APIs, including the one proposed by JEP-8280389. Here's a comparison.

That's a lot right arrow operators just to implement a simple Hello World program (5). I can't even begin to imagine how difficult it might be to generate anything more interesting than this. Here's a comparison against a classfile API which is designed to be easy to use: https://github.com/cojen/Maker/wiki/JEP-8280389

For the code generation phase, it might be easier to bypass emitting a text-based assembly format and just use the ASM library directly. If you want something easier, I wrote a code generation library specifically for that purpose: https://github.com/cojen/Maker It also includes an example "Mini-C" language compiler.