DocumentFilter - Replacing text in a JTextBox

Question

I am trying to replace the text in a text box that has been filtered to only accept characters 0 to 9. I'm using String's here because I need the 0's to remain as part of the value. ex the first value would be 001 so it must be replaced by 002. It seems to work when I don't require a filter that forces numbers only. The initial check works - I'm able to type in 001 but then I submit 001 doesn't change to 002. Any help would be great.

THE CODE TRYING TO REPLACE THE TEXT ...

    `if(pageBox.isSelected()){
    String num;
    System.out.println(newPage);
    int p = Integer.parseInt(newPage);
    p++;
    if(p < 10){
    num = ("00" + Integer.toString(p));
    }
    else if(p >= 10 && p < 100){
    num = ("0" + String.valueOf(p));
    }
    else{
    num = (String.valueOf(p));
    }
    pageField.setText(num);

    }
    else{
    pageField.setText("");
    }`

THE FILTER I'M USING //SETS CHARACTER LIMIT & ALLOWS NUMERIC VALUES ONLY

`class SizeAndStringNumFilter extends DocumentFilter {
private int limit;

    public SizeAndStringNumFilter(int limit) {
        this.limit = limit;
    }
    
    @Override
    public void insertString(FilterBypass fb, int offs, String str, AttributeSet a) throws BadLocationException {
    
        Document doc = fb.getDocument();
        StringBuilder sb = new StringBuilder();
        sb.append(doc.getText(0, doc.getLength()));
        sb.insert(offs, str);
    
        if (test(sb.toString())) {
            if ((fb.getDocument().getLength() + str.length()) <= limit)
                super.insertString(fb, offs, str, a);
            else
                Toolkit.getDefaultToolkit().beep();
        }
        else {
            //WARN - only numeric values allowed
        }

}
private boolean test(String text) {

        int i = text.length() - 1;
        boolean check = text.charAt(i) >= '0' && text.charAt(i) <= '9';
        
        if(!check){
            //WARN USER
            Toolkit.getDefaultToolkit().beep();
        }
        
        return check;
    
    }
    
    @Override
    public void replace(FilterBypass fb, int offs, int length, String str, AttributeSet a) throws BadLocationException {
        Document doc = fb.getDocument();
        StringBuilder sb = new StringBuilder();
        sb.append(doc.getText(0, doc.getLength()));
        sb.insert(offs, str);
    
        if (test(sb.toString())) {
            if ((fb.getDocument().getLength() + str.length()) <= limit)
                super.insertString(fb, offs, str.toUpperCase(), a);
            else
                Toolkit.getDefaultToolkit().beep();
        }
        else {
            //WARN - only numeric values allowed
        }   
    }

}`

**EDIT I've found the culprit - The document filter doesn't replace the text it appends it. Not sure how to combat this

**EDIT2 Problem solved, once I figured out the issue I just had to add a second if statement for > limit if((fb.getDocument().getLength() + str.length()) - length > limit) super.replace(fb, offs, length, str.substring(0, limit-fb.getDocument().getLength()).toUpperCase(), a);