Document filter that limits the length of the input to a set number of characters

LengthLimitDocumentFilter.java

import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.DocumentFilter;

public class LengthLimitDocumentFilter extends ChainedDocumentFilter {
    
    private int maxCharacters;

    public LengthLimitDocumentFilter(DocumentFilter filter, int maxChars) {
        super(filter);
        maxCharacters = maxChars;
    }

    public LengthLimitDocumentFilter(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 {
            provideErrorFeedback();
        }
    }

    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 {
            provideErrorFeedback();
        }
    }
    
}