What is system.in

Question

Consider this Scanner input example.

Scanner user_input = new Scanner( System.in );

Here Scanner is the CLASS. user_input is the OBJECT under Scanner class. What is (System.in)? Is it a parameter passed or a object under Scanner class?.

Consider another example.

dog dog1 = new dog(25)

Here I have set dog class to accept size as a parameter.

What exactly is System.in?

Answer 1

Scanner class accepts input stream as a parameter and System class have a static variable in which is of type InputStream. System.in gives you a instance of of type InputStream.

Check this doc of public static final InputStream in

The "standard" input stream. This stream is already open and ready to supply input data.