JTextField Validation with integers

Question

I am trying to validate integer values from a JTextField. I want to make sure the user only enters integer values between a set range. I tried working with a JFormattedTextField but so far no luck.

Answer 1

One good option is to use an InputVerifier - your text field will not yield focus unless the input conditions are met. A JFormattedTextField won't do here since your restriction is not solely format, but also mathematical.

public class NumRange extends JFrame {

    public static void main(String[] args) {

        new NumRange();
    }

    NumRange() {

        final int MIN = 0;
        final int MAX = 100;

        JTextField textField = new JTextField();
        textField.setInputVerifier(new InputVerifier() {

            @Override
            public boolean verify(JComponent input) {
                String text = ((JTextField) input).getText();
                int num;
                try {
                    num = Integer.parseInt(text);
                } catch (NumberFormatException e) {
                    return false;
                }
                if (num <= MAX && num >= MIN)
                    return true;
                return false;
            }
        });

        getContentPane().add(textField);
        getContentPane().add(new JTextField(), BorderLayout.PAGE_END);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        pack();
        setVisible(true);
    }
}

Try to switch focus to the bottom text field after entering various inputs to the top one.