Java Swing：在JPanel上向用户显示验证规则

Question

I have a JPanel which contains a number of JTextField(s) that have a length limit of a few characters (implemented by a custom PlainDocument).

I want to display a text in red font at the top left of the panel saying, "**Fields allow a max of 20 characters.".

Two options that I am considering so far is adding a TitledBorder or a JLabel. What is the best way to do this?

Thank you.

Answer 1

You can add one more JLabel to the TextField, wich you can setVisible, when needed.

JTextField t = new JTextField();
    t.setBounds(0, 0, 200, 75);
    frame.add(t);

    JLabel l = new JLabel();
    l.setText("only 20 Character");
    l.setForeground(Color.red);
    l.setBounds(0, 0, 100, 25);
    t.add(l);

Thats how I would do it.