what is classloader in java.

Classloader is a subsystem of jvm that is used to load class and interface.
There are many type of class loader such as Extension classloder,system classloader.

What is JIT Complier

JIT  is stand for just in time compiler it is used to increase the  performance.JIT compile part of bytecode at the same time that have same functionality  thus reduce the time needed for the compilation of the code.