What does System.in refer to by default?

Question

The read() method is declared abstract in InputStream class. But we are able to read from keyboard using System.in.read().

My question is that 'in' is a reference of InputStream class. So to use read() method in has to refer to some subclass of InputStream.

To what class does 'in' refer to by default? Can we write a code to find answer to this question?

Answer 1

To answer your specific question: Yes, you can find out the class of System.in by writing code.

This is the application you are looking for:

public class SystemDotInClassFinder {
    public static void main(String[] args) {
        System.out.println(System.in.getClass().getName());
    }
}

Running this script produces:

java.io.BufferedInputStream