what is libcore and its role in android?

Question

I am new to android and java. I have been looking at the source code and think faintly that maybe it is a Java implementation.

Answer 1

According to this slide deck from 2016, Libcore is Google's implementation of some core Java libraries such as java.net, java.util, java.icu (Unicode), java.math, java.reflect, and possibly more. Libcore also allows for POSIX system calls from Java.

Libcore's master branch can be found here. Most of Google's implementation is found in folder luni , but libcore also mixes with Oracle code. For example, Oracle's JNI implementation from OpenJDK is used in Android in folder ojluni. So libcore replaces some functionality from OpenJDK, but not all.