JTextField Document for integers

The class below is used by a JTextField and is intended to allow integers only. However, what it does is allow only integers >= 0 because it will not allow a "-" to be typed for a negative integer. How can I get it to accepts negative integers, too?

/**
 * This document only allows integer values to be added to it.
 */
static class IntegerDocument extends PlainDocument {

	public void insertString(int offset, String string, AttributeSet attributeSet) throws BadLocationException {

	if (string != null) {
		try {
			Integer.decode(string);
			super.insertString(offset, string, attributeSet);
		}
		catch (NumberFormatException ex) {
			System.out.println ("not a digit");
			Toolkit.getDefaultToolkit().beep();
		}
	} // end if
}
} // end IntegerDocument

Open in new window

LVL 1
allelopathAsked:
Who is Participating?
 
ProtuhjCommented:
use Integer.parseInt() rather than decode... decode can only take positive numbers..

http://forums.sun.com/thread.jspa?threadID=5437277
0
 
allelopathAuthor Commented:
Good idea, but that doesn't work, at least in my case. The insertString() method is called every time a character is typed, so if the user intends to enter "-1", insertString() is called for the - , and both decode() and parseInt() throw the NumberFormatException.

I guess what I have to do is check for the -, like so:

if (string != null) {
      try {
            // let minus sign pass through
            if (! string.equals("-")) {
                  Integer.decode(string);
            }
            super.insertString(offset, string, attributeSet);
0
 
objectsCommented:
you should be parsing the result string, not just the string entered
and you need to treat "-" as a special case
0
Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

All Courses

From novice to tech pro — start learning today.