Further investigate a little bit, seems like Minecraft 1.12.2 vanilla runs perfectly on Java 11, even on Java 15 or new. The issue is caused by forge, which used a lot of dirty skills not allowed in Java 11. I seen a method to make forge work with java 11 by using javaagent, however I can't find trusted source to make it work. The only one I found is compiled for bytecode version 57, which is Java13. I still prefer the LTS version in daily development, so I didn't try with jdk13.
Thus I'll just install a Oracle jre1.8 and wait mod developer to adapt for 1.13+, which I noticed since that version forge is rewritten to support newer Java.
Anyway, Java edition is better than C++ edition, though it brings me so much trouble. At least I won't pay for my skin and resource package.
@skyblond At least the Java edition has the best modpacks in my opinion. So totally worth it even though it's not the best language.
