Limit the Characters in the text field using document listner

Question

How to limit the number of characters entered in a JTextField using DocumentListener?

Suppose I want to enter 30 characters max. After that

Answer 1

You'll want to use a DocumentFilter for this purpose. As the applies, it filters documents.

Something like...

public class SizeFilter extends DocumentFilter {

    private int maxCharacters;    

    public SizeFilter(int maxChars) {
        maxCharacters = maxChars;
    }

    public void insertString(FilterBypass fb, int offs, String str, AttributeSet a)
            throws BadLocationException {

        if ((fb.getDocument().getLength() + str.length()) <= maxCharacters)
            super.insertString(fb, offs, str, a);
        else
            Toolkit.getDefaultToolkit().beep();
    }

    public void replace(FilterBypass fb, int offs, int length, String str, AttributeSet a)
            throws BadLocationException {

        if ((fb.getDocument().getLength() + str.length()
                - length) <= maxCharacters)
            super.replace(fb, offs, length, str, a);
        else
            Toolkit.getDefaultToolkit().beep();
    }
}

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