What is mean abstraction in java??

Answer 1

Abstraction is a generic term that applies to many languages.

Check out this for the meaning:
https://en.m.wikipedia.org/wiki/Abstraction_(software_engineering)

Answer 2

Abstraction is the process of hiding the implementation details and showing only functionality to the user.
And in java abstraction can be achieved using Abstract class and Interface.

Answer 3

data types. both built-in as well as user defined.