Legal issues against tweaking Swing sources?

Question

Hello,
I needed in my application a TableCellRenderer which would behave exactly like a default one, except it would cut out the left part of the text when it is too long to fit into table cell (that is, it would transform, say, "something here" to "...ing here" instead of "somethin...")
I looked at DefaultTableCellRenderer, but found no method which would satisfy my needs. So there was nothing to it but to write a custom renderer. But how? Further investingation showed that Swing uses the method javax.swing.SwingUtilities.layoutCompoundLabel internally to create the abbreviation at need. So, I grabbed Swing sources which come bundled with the SDK, took the code of that method along with some others (if it were only possible to avoid copy-pasting...), reworked slightly to fit my needs and packed into a neat subclass.
It does work. But my question is: are there any legal issues regarding this approach? What, if anything, must I do to be fair with the license? Or is it not possible at all?
The application is a non-commercial (although I do get paid for it), scientific project which is not currently GPL'ed, but may become so in the future.
Sincerely,
Daniel Janus

Answer 1

Are you sure you want to do that. If you do something like that, then when you distribute your application, your clients will have to have your version of the code. And, what about when sun upgrades the class you are modifying. You would have to modify the new one if it still behaved the sameway. What a maintainable nightmare.
Personally, I normally write my own JTable and TableModel as well as my own editors and renderers. I think I use the default cell renderer for String data types though. I don't remember ever seeing it display in the manner you describe. You could always increase the cell size if you want. Just for fun's sake, let me give you an example of a CellRenderer:package some.package.name;
import javax.swing.table.*;
import javax.swing.*;
import java.text.*;
import java.awt.*;
import java.util.*;
import java.io.Serializable;
* The cell renderer for Date and DateTime data types.
* Used to display formatted Date data.  Must be registered with
* a particular table.  Use the following code to do this.<BR><BR>
* <code>table.setDefaultRenderer(Date.class, new SomeDateRenderer());</code>
* from within your JTable.
* @author your name here
public class SomeDateRenderer extends DefaultTableCellRenderer implements Serializable {
     * Default Date Format String for formatting dates in this renderer.
     public static final String DATE_FORMAT_STR = "MM/dd/yyyy";
     * Default Time Format String for formatting times in this renderer.
     public static final String TIME_FORMAT_STR = "HH:mm";
     * Default DateTime Format String for formatting dates in this renderer.
     public static final String DATETIME_FORMAT_STR = DATE_FORMAT_STR+" "+TIME_FORMAT_STR;
     * Constructor.
   public SomeDateRenderer() {
          super();
          setHorizontalAlignment(SwingConstants.CENTER);
     }//end constructor
     * (override) Standard getTableCellRendererComponent.
     public Component getTableCellRendererComponent(JTable table, Object value,
               boolean isSelected, boolean hasFocus, int row, int column) {
        super.getTableCellRendererComponent(table,value,isSelected,hasFocus,row,column);
      if (value != null && !value.equals("")) {
         String formatStr = null;
         if (value instanceof java.util.Date) {
            setText(new SimpleDateFormat(DATE_FORMAT_STR).format(value));                    
         } else if (value instanceof java.sql.Time) {
            setText(new SimpleDateFormat(TIME_FORMAT_STR).format(value));
         } else if (value instanceof java.sql.Timestamp) {
            setText(new SimpleDateFormat(DATETIME_FORMAT_STR).format(value));               
      } else {
         setValue(value);
        return this;
   }//end getTableCellRendererComponent method
}//end SomeDateRendererAnyways, you can write a renderer to be anything you want. This is just a rudimentary example. I hope it helps.