Reading each keystroke from a console app?

Question

I'm using Sun JDK 1.3.0_02 on RedHat Linux 7.1.
I've written a console application (no GUI, no Swing), from which I need to read each keystroke from the keyboard as it is typed.
My loop basically waits (blocks) on System.in.read(), and disposes of each byte as it is read.
Unfortunately, the way the app executes, my Java app doesn't seem to be given any keyboard input until the user presses ENTER. In addition, each keystroke is echoed to the console display, which I don't want.
Can anyone point me in the right direction to solve this? I can't use any GUI components as this needs to be a console app.
Thank you,
Bryan

Answer 1

This can be fixed with a tiny JNI program. As long as the 'c' call getch() works the same on all platforms:
// The Java class
import java.io.*;
public class ConsoleInputStream extends InputStream
    public native int read();
    static
        System.loadLibrary("ConsoleInputStream");
// The JNI header
/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class ConsoleInputStream */
#ifndef _Included_ConsoleInputStream
#define _Included_ConsoleInputStream
#ifdef __cplusplus
extern "C" {
#endif
#undef ConsoleInputStream_SKIP_BUFFER_SIZE
#define ConsoleInputStream_SKIP_BUFFER_SIZE 2048L
/* Inaccessible static: skipBuffer */
* Class:     ConsoleInputStream
* Method:    read
* Signature: ()I
JNIEXPORT jint JNICALL Java_ConsoleInputStream_read
  (JNIEnv *, jobject);
#ifdef __cplusplus
#endif
#endif
// The JNI 'C' code
#include "..\classes\generated source\consoleInputStream.h"
#include "conio.h"
JNIEXPORT jint JNICALL Java_ConsoleInputStream_read(JNIEnv * env, jobject obj)
    return getch();
// The test program
public class Console
    public static void main(String[] args)
        try
            System.setIn(new ConsoleInputStream());
            while(true)
                int ch=System.in.read();
                if(ch=='\r')
                    break;
                else
                    System.out.print((char)ch);
        catch(Exception ex)
            ex.printStackTrace();
// the build script (Windows)
cl -I\j2sdk1.4.0\include -I\j2sdk1.4.0\include\win32 ConsoleInputStream.cpp /MD /LD user32.lib /link/out:..\classes\ConsoleInputStream.dllHope this helps :)