What does System.in.read actually return?

Question

What does :

System.in.read()

return ? The documentation says :

Returns: the next byte of data, or -1 if the end of the

Answer 1

System.in.read() reads just one byte.

49 is the Unicode point value for 1.

Try to print:

System.out.println((char)49);

This will help you to understand it more.

Answer 2

49 is the ASCII value of the char 1. It is the value of the first byte.

The stream of bytes that is produced when you enter 10Enter on your console or terminal contains the three bytes {49,48,10} (on my Mac, may end with 10,12 or 12 instead of 10, depending on your System).

So the output of the simple snippet

int b = System.in.read();
while (b != -1) {
    System.out.println(b);
    b = System.in.read();
}

after entering a 10 and hitting enter, is (on my machine)

49
48
10

Answer 3

When you enter 10, it is not read as an integer but as a String or, more precisely here, an array of bytes.

49 is the ASCII code for the character 1.