How to readLine with echo in Java?

Question

I would like to use a BufferedReader with a kind of readLine() (or similar) that can return an echo for every keystroke pressed.

It's for a remote terminal. Other way to ask it is how is implemented a console in java.

This is what came to mind but is too ugly. Is there any known library that implement something like this?

while(condition) {

    nByteRead = in.read(buffer);

    if (nByteRead != -1) {

        //  ECHO
        out.write(buffer, 0, bytes_read);                      

        //  read bytes till NEW_LINE...                            
        //  etc...!                            
    }                           
}

Of course I could encapsulate this behaviour in some thread and go on with a library for this, I just wonder if there is some wheel already invented.

Thanks for any hint!

score 1 · Answer 1 · edited May 23 '17 at 09:59

1

Most terminals, including the default terminals in Ubuntu and Windows (I believe) won't pass on the characters to the JVM until the user hits return. (I.e., it is buffered on a full-line basis on a lower level in the system.)

If you need to read one character at a time from the terminal, you'll have to go with a lower level system library.

Related question:

Why can't we read one character at a time from System.in?

(disclamer, I'm not completely sure I understood your question correctly.)

edited May 23 '17 at 09:59

Community

1
1

answered Sep 01 '11 at 12:03

aioobe

413,195
112
811
826

I think you understood it, but I don't want to read from the terminal, I want to read from a socket, sending "echo" to user, so he see that whatever is typing has reached the server. – Hernán Eche Sep 01 '11 at 12:14
Is the client written in java? – aioobe Sep 01 '11 at 12:19
No, client is not necesarily Java – Hernán Eche Sep 01 '11 at 12:22

score 1 · Answer 2 · answered Sep 01 '11 at 12:04

1

There's:

JLine: http://jline.sourceforge.net/
Java Curses: http://sourceforge.net/projects/javacurses/

answered Sep 01 '11 at 12:04

Bart Kiers

166,582
36
299
288

I'll try JLine but I see it uses some dll, and work differently for windows and linux. I see there is no Java standard way to do this, so perhaps I'll code it by hand, thanks – Hernán Eche Sep 01 '11 at 12:18

How to readLine with echo in Java?

2 Answers2