JCP
Java Community Process https://www.jcp.org/en/home/index
The mechanism for developing technical specifications for Java.
JSR
Java Specification Request https://jcp.org/en/jsr/overview
Proposed and actual specification requests for Java features and technology.
JEP
Java Enhancement Proposal http://openjdk.java.net/jeps/1
A JEP is a proposal for a non-trivial enhancement to be added to the OpenJDK roadmap. It does not supplant the JCP and JEPs may create parallel JSRs or modify existing ones.
FFI
A Mechanism by which one language can call methods or functions implemented in another language. The FFI for Java is Java Native Interface (JNI).