Limit JTextField character input

Question

So I searched all over internet and in every single topic I found this solution for limitting JTextField input.

public class FixedDocument extends PlainDocument {
  private int limit;
  // optional uppercase conversion
  private boolean toUppercase = false;

  FixedDocument(int limit) {
   super();
   this.limit = limit;
   }

  FixedDocument(int limit, boolean upper) {
   super();
   this.limit = limit;
   toUppercase = upper;
   }

  public void insertString (int offset, String  str, AttributeSet attr) throws BadLocationException {
   if (str == null){
       return;
   }
    if ((getLength() + str.length()) <= limit) {
     if (toUppercase) str = str.toUpperCase();
     super.insertString(offset, str, attr);
     }
   }
}

but I have a problem with that code. This code line "super.insertString(offset, str, attr);" gives me error:

no suitable method found for insertString(int,java.lanf.String,javax.print.attribute.AttributeSet)
 method javax.swing.text.PlainDocument.insertString(int,java.lang.String,javax.text.AttributeSet) is not applicable
  (actual argument javax.printattribute.AttributeSet cannot be converted to javax.swing.text.AttributeSet by method invocation conversion)

anyone got any ideas what I am doing wrong here?

Answer 1

Your problem is that your importing the wrong AttributeSet class. You are importing javax.print.attribute.AttributeSet, when you should be importing javax.swing.text.AttributeSet, and the error message pretty much tells you this. Again, myself, I'd use a DocumentFilter for this as that is what it was built for.