Thread: Java mutex causing "missed input" compared to busy loop?

Hey everyone, I'm writing a Java program that interfaces with a C program on my Linux server (it's a client/server chat program). Right now, I'm implementing a blocking feature for the input to block until the user presses "Enter" before sending the input to the server. To do this, I have two choices: a busy loop, and a mutex. The mutex is obviously the best alternative, but I'm running into an issue where sometimes the input just won't send to the server at *all*. With the busy loop, though, I just unset a flag and it works fine.

Busy loop:

String line = "";
// Block until we receive some input.
while (!this.inputField.isReady()) {
}
line = this.inputField.getText();
this.writefp.write(line + "\n");
this.writefp.flush();
this.inputField.setReady(false);

So, all I need to do in the textfield (in a keylistener) is:

...
public void keyPressed(KeyEvent e) {
  if (e.getKeyCode() == KeyEvent.VK_ENTER) {
    ready = true;
    setText("");
  }
}
...

So, yes, this works. My mutex solution isn't so lucky:

while (!this.inputField.isReady()) {
  synchronized(this.inputField.mutex) {
    try {
      this.inputField.mutex.wait();
    } ... //redacted for simplicity
  }
}

And the notifier:

...
ready = true; 
// This is in the TextField class.
synchronized(this.mutex) {
  this.mutex.notify();
}
setText("");
...

Maybe I'm misunderstanding a fundamental piece of Java's synchronization capabilities (this is much easier in C...). the mutex is just a standard Object, following online examples. Any help would be greatly appreciated.