StringBuffer behavior in LWJGL

Question

Okay, I've been programming in Java for about ten years, but am entirely new to LWJGL. I have a specific problem whilst attempting to create a text console. I have built a class meant to abstract input polling to it, which (in theory) captures key presses from the Keyboard object and appends them to a StringBuilder/StringBuffer, then retrieves the completed string after receiving the ENTER key.

The problem is, after I trigger the String return (currently with ESCAPE), and attempt to print it to System.out, I consistently get a blank line. I can get an appropriate string length, and I can even sample a single character out of it and get complete accuracy, but it never prints the actual string.

I could swear that LWJGL slipped some kind of thread-safety trick in while I wasn't looking.

==UPDATE==

I've now determined that a null value was appended at the beginning of my StringBuffer. The problem can (sloppily) be solved with a command.delete(0, 1) line, freeing the actual String data. However, I don't know how that null got in there to begin with. If anyone sees it before I do, please let me know.

Here's my code:

static volatile StringBuffer command = new StringBuffer();

@Override
public void chain(InputPoller poller) {
    this.chain = poller;
}

@Override
public synchronized void poll() {
    //basic testing for modifier keys, to be used later on
    boolean shift = false, alt = false, control = false, superkey = false;

    if(Keyboard.isKeyDown(Keyboard.KEY_LSHIFT) || Keyboard.isKeyDown(Keyboard.KEY_RSHIFT))
        shift = true;
    if(Keyboard.isKeyDown(Keyboard.KEY_LMENU) || Keyboard.isKeyDown(Keyboard.KEY_RMENU))
        alt = true;
    if(Keyboard.isKeyDown(Keyboard.KEY_LCONTROL) || Keyboard.isKeyDown(Keyboard.KEY_RCONTROL))
        control = true;
    if(Keyboard.isKeyDown(Keyboard.KEY_LMETA) || Keyboard.isKeyDown(Keyboard.KEY_RMETA))
        superkey = true;

    while(Keyboard.next())
        if(Keyboard.getEventKeyState()) {
            command.append(Keyboard.getEventCharacter());
        }

        if (Framework.isConsoleEnabled() && Keyboard.isKeyDown(Keyboard.KEY_ESCAPE)) {
            System.out.println("Escape down");
            System.out.println(command.length() + " characters polled"); //works
            System.out.println(command.toString().length()); //works
            System.out.println(command.toString().charAt(4)); //works
            System.out.println(command.toString().toCharArray()); //blank line!
            System.out.println(command.toString()); //blank line!

            Framework.disableConsole();
        }

        //TODO: Add command construction and console management after that
    }
}

Maybe the answer's obvious and I'm just feeling tired, but I need to walk away from this for a while. If anyone sees the issue, please let me know. This machine is running the latest release of Java 7 on Ubuntu 12.04, Mate desktop environment.

Many thanks.

Answer 1

Judging with the code you provided, your STDOUT Stream likely isn't what you expect it to be due to a control character.

Try using a System.out.flush() after your System.out.print()

Let me know if this helps.

Answer 2

Solution found. To toggle the console mode, I use the tilde key ("~"). This requires a shift, and the grave character ("`", next to the numbers). After I release tilde, I generally still have the shift key down, which, incidentally, is a type of key event. Shift itself is not responsible for a proprietary character, yet is fully valid otherwise. Thus, when I request the character, I receive null, and append it to the ArrayList contained in StringBuffer. A little defensive programming will easily solve this.