How to read a single char from the console in Java (as the user types it)?

user_70616 0
Viewed 159299

Is there an easy way to read a single char from the console as the user is typing it in Java? Is it possible? I've tried with these methods but they all wait for the user to press enter key:

char tmp = (char) System.in.read();
char tmp = (char) new InputStreamReader(System.in).read ();
char tmp = (char) System.console().reader().read();           // Java 6

I'm starting to think that System.in is not aware of the user input until enter is pressed.

console input java
7 Answers

What you want to do is put the console into "raw" mode (line editing bypassed and no enter key required) as opposed to "cooked" mode (line editing with enter key required.) On UNIX systems, the 'stty' command can change modes.

Now, with respect to Java... see Non blocking console input in Python and Java. Excerpt:

If your program must be console based, you have to switch your terminal out of line mode into character mode, and remember to restore it before your program quits. There is no portable way to do this across operating systems.

One of the suggestions is to use JNI. Again, that's not very portable. Another suggestion at the end of the thread, and in common with the post above, is to look at using jCurses.

user_844160

I' ve done it using jcurses...

import jcurses.system.InputChar;
import jcurses.system.Toolkit;

//(works best on the local machine when run through screen)
public class readchar3 {
    public static void main (String[] args)
        {
            String st;
            char ch;
            int i;
            st = "";
            ch = ' ';
            i = 0;
            while (true)
                {
                        InputChar c = Toolkit.readCharacter();
                    ch = c.getCharacter();
                    i = (int) ch;
                    System.out.print ("you typed " + ch + "(" + i + ")\n\r");
                    // break on '#'
                    if (ch == '#') break;
                }
            System.out.println ("Programm wird beendet. Verarbeitung kann beginnen.");
        }
}
user_155954780

See This

It calls _getch() function from c to read a single char without hitting Enter

user_163209160
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