Collar mod

//TODO general description about collar-mod
maybe put the current stuff into a BUILD.md and use README as a user-manual

Compiling submodules with Java 1.8

Set it up in IntelliJ:

Set the project SDK to Java 16 in Project Structure

Then
if you want to compile Forge 1.12 with J1.8:
Set forge-1.12, forge-1.12.main and forge-1.12.test JDK to Java 1.8.

Apparently every module can be compiled with JDK 16, including forge-1.12

Debug

1.16
Forge 1.16 debug won't launch, even if it can compile with JDK16

Fix it by adding this to the launch arguments:
--add-exports=java.base/sun.security.util=ALL-UNNAMED --add-opens=java.base/java.util.jar=ALL-UNNAMED
Or you can just make it to debug with old jdk.

1.12
Well, that is a bit complicated. Hope The Forge God, LexManos will fix it.
now: forge-1.12/README

It has been fixed.
Just set the debug Java version to Java 1.8 and the module to collar-mod.forge-1.12.main
And press run/debug

Warning:

Java ByteBuffer had some changes after J1.8, mostly the return type.
Some function, what had Buffer return type, has ByteBuffer return in J9+.
These can cause errors (NoSuchMethodError), when you compile with J16, and then you use that in J1.8
(targetCompatibility = 1.8 does not help)
You can avoid these by casting the ByteBuffer to Buffer before invoking the method.

ByteBuffer buf;

//J1.8: public Buffer position(int newPosition);
//19+ : public ByteBuffer position(int newPosition);

        ((Buffer)buf).position(someInt);
//It will search for a method, what returns with Buffer. A method what returns with ByteBuffer will be accepted.

        buf.position(someInt);
//It will search for a function, what returns with ByteBuffer, but there is what returns with Buffer.

Using the first one, will solve the issue.
Example in: [KosmX/emotes]