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Editorial Team
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Asked: 2026-05-17T20:26:40+00:00

The program below prints each character written on standard in, but only after a

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The program below prints each character written on standard in, but only after a new-line has been written (at least on my system!).

public class Test {
    public static void main(String[] args) throws java.io.IOException {
        int c;
        while ((c = System.in.read()) != -1)
            System.out.print((char) c);
    }
}

This prevents people from writing stuff like “Press any key to continue” and forces something like “Press enter to continue.”

  • What is the underlying reason for this?
  • Is it a limitation of Java?
  • Is this behavior system-dependent (I’m on Ubuntu)? How does it work on Mac? Windows?
  • Is it dependent on the specific terminal I run the application in? (For me it behaves like this in Eclipse and in gnome-terminal)
  • Is there a workaround?
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1 Answer

  1. Editorial Team

    What is the underlying reason for this?

    Most terminals is line buffered by default, Java does not receive input until a newline.

    Is it a limitation of Java?

    Some ancient terminals might only have line-buffered input; though it should be possible to disable buffering in most modern terminal.

    Is this behavior system-dependent (I’m on Ubuntu)? How does it work on Mac? Windows?

    Yes.

    Is it dependent on the specific terminal I run the application in? (For me it behaves like this in Eclipse and in gnome-terminal)

    Yes.

    Is there a workaround?

    There are platform specific hacks. curse in Linux and Unix-like platforms, and getch() in Windows. I’m not aware of any cross-platform way.

    related: Why “Press any key to continue” is bad idea:

    alt text

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