Editable JCombobox cell editor length limit

Question

Hi All,
I have an editable JCombobox as a celleditor to one of the column in JTable, How do I limit the characters in the cell editor?
Thanks

Answer 1

A JComboBox uses a JTextField as it's cell editor. You should read up on how you would do this for a normal JTextField by using a custom Document:
http://java.sun.com/docs/books/tutorial/uiswing/components/generaltext.html
Here's an example using JComboBox. I haven't tried it in a JTable but I assume it should work.
import java.awt.*;
import javax.swing.*;
import javax.swing.text.*;
import javax.swing.plaf.basic.*;
public class ComboBoxNumericEditor extends BasicComboBoxEditor
     public ComboBoxNumericEditor(JComboBox box)
          editor.setDocument( new NumericListDocument(box.getModel()) );
     public static void main(String[] args)
          String[] items = { "one", "two", "three", "four" };
          JComboBox list = new JComboBox( items );
          list.setEditable( true );
          list.setEditor( new ComboBoxNumericEditor( list ) );
          JFrame frame = new JFrame();
          frame.getContentPane().add( list );
          frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
          frame.pack();
          frame.setLocationRelativeTo( null );
          frame.setVisible( true );
     class NumericListDocument extends PlainDocument
          ListModel model;
          public NumericListDocument(ListModel model)
               this.model = model;
          public void insertString(int offset, String text, AttributeSet a)
               throws BadLocationException
               //  Accept all entries in the ListModel
               for (int i = 0; i < model.getSize(); i++)
                    Object item = model.getElementAt(i);
                    if (text.equals( item.toString() ))
                         super.insertString(offset, text, a);
                         return;
               //  Build the new text string assuming the insert is successfull
               String oldText = getText(0, getLength());
               String newText =
                    oldText.substring(0, offset) + text + oldText.substring(offset);
               //  Edit the length of the new string
               if (newText.length() > 2)
                    Toolkit.getDefaultToolkit().beep();
                    return;
               //  Only numeric characters are allowed in the new string
               //  (appending the "0" will allow an empty string to be valid)
               try
                    Integer.parseInt(newText + "0");
                    super.insertString(offset, text, a);
               catch (NumberFormatException e)
                    Toolkit.getDefaultToolkit().beep();
}