Restricting JTextField input to Integers [duplicate]

Answer 1

I used to use the Key Listener for this but I failed big time with that approach. Best approach as recommended already is to use a DocumentFilter. Below is a utility method I created for building textfields with only number input. Just beware that it'll also take single '.' character as well since it's usable for decimal input.

public static void installNumberCharacters(AbstractDocument document) {
        document.setDocumentFilter(new DocumentFilter() {
            @Override
            public void insertString(FilterBypass fb, int offset,
                    String string, AttributeSet attr)
                    throws BadLocationException {
                try {
                    if (string.equals(".")
                            && !fb.getDocument()
                                    .getText(0, fb.getDocument().getLength())
                                    .contains(".")) {
                        super.insertString(fb, offset, string, attr);
                        return;
                    }
                    Double.parseDouble(string);
                    super.insertString(fb, offset, string, attr);
                } catch (Exception e) {
                    Toolkit.getDefaultToolkit().beep();
                }

            }

            @Override
            public void replace(FilterBypass fb, int offset, int length,
                    String text, AttributeSet attrs)
                    throws BadLocationException {
                try {
                    if (text.equals(".")
                            && !fb.getDocument()
                                    .getText(0, fb.getDocument().getLength())
                                    .contains(".")) {
                        super.insertString(fb, offset, text, attrs);
                        return;
                    }
                    Double.parseDouble(text);
                    super.replace(fb, offset, length, text, attrs);
                } catch (Exception e) {
                    Toolkit.getDefaultToolkit().beep();
                }
            }
        });
    }