How to check KeyListener input?

In java.awt.event.Ke开发者_如何学运维yListener, how do I check if the user enters "+" or "- "?

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Here's a code example of how to do this:

    TextField field = new TextField();
    field.addKeyListener(new KeyListener() {
        public void keyTyped(KeyEvent e) {
            final char aChar = e.getKeyChar();
            if (aChar == '+') {
                System.out.println("+ was typed");
            }
            if (aChar == '-') {
                System.out.println("- was typed");
            }
        }

        public void keyPressed(KeyEvent e) {
        }

        public void keyReleased(KeyEvent e) {
        }
    });