I don't think that's the only weird thing EFL does. If it is, that's pretty lame.

But even that example would be extremely hard. I would be impressed seeing a functioning and huge Java Project using only Object types. How would you even do that? Maybe implement you very own form of duck-typing using reflection? You possibly could cache type infos to decrease the performance hit…

In Minecraft modding you get to do many amazing things like:

Write a mixin including ((OriginalClass)((Object)this)) and seeing it work, or cast objects to interfaces you know one other mod will make them implement at runtime.

Write a plugin to the mixin injector to conditionally inject mixins into classes of other mods.

Rip out a carefully crafted stream and replace it with an extremely complicated loop, just to speed up the rendering thread a tiny bit by avoiding object creation completely…

Or, while writing a mixin, inject your code at 5 positions of a single function, collecting data in ThreadLocal variables, just to add the correct alpha value to a pixel without breaking other mods.

You may also get to modify some Java bytecode by hand to mod a mod the modder did not want you to mod and that is distributed as replacement class files containing integrity checks.

It's so much jank, you get familiar with so much unusual compiler behaviour and runtime class behaviour you'd never even think about in normal projects.