How can I print what is read by intputstream immediately?

Question

This is the code I have:

import java.io.DataInputStream;
import java.io.InputStream;

public class TestClass {
    public static void main(String[] args) throws Exception {
        InputStream inputStream = new DataInputStream(System.in);
        int read = inputStream.read();
        System.out.println(read);
    }
}

When I run this code inputStream will wait for input from the standard input which is fine. When I type 'a' in keyboard, I expect 97 to be printed immediately in the console. However this code requires me to hit 'Enter' after I type 'a'.

If I simply hit 'Enter' integer 10 will be shown in the console.

How can I modify the code so that as soon as I hit 'a' in the keyboard I see the integer 97? What is so special about the Enter button in this case? Why do I need to hit Enter?

Answer 1

Sadly there's no way to do this with the console in Java. No matter whether you use a java.util.Scanner or a kind of java.io.InputStream (including System.in directly), the Enter key is always the trigger for input to be received.

Consider using a graphical user interface like Swing (definition on wikipedia), where you can fulfill your input requirements by hooking up a KeyListener to a text box.