public class JavaSourceFileLayerPaletteFactory {

    *//Name of the folder in the layer.xml file that is the root of the palette:*
    public static final String JAVA_PALETTE_FOLDER = "JavaPalette";

    private static PaletteController palette = null;

    public JavaSourceFileLayerPaletteFactory() {
    }

    public static PaletteController createPalette() {
        try {
            if (null == palette)
                palette = PaletteFactory.createPalette(JAVA_PALETTE_FOLDER, new MyActions());
            return palette;
        } catch (IOException ex) {
            Exceptions.printStackTrace(ex);
        }
        return null;
    }

    private static class MyActions extends PaletteActions {

        *//Add new buttons to the Palette Manager here:*
        public Action[] getImportActions() {
            return null;
        }

        *//Add new contextual menu items to the palette here:*
        public Action[] getCustomPaletteActions() {
            return null;
        }

        *//Add new contextual menu items to the categories here:*
        public Action[] getCustomCategoryActions(Lookup arg0) {
            return null;
        }

        *//Add new contextual menu items to the items here:*
        public Action[] getCustomItemActions(Lookup arg0) {
            return null;
        }

        *//Define the default action here:*
        public Action getPreferredAction(Lookup arg0) {
            return null;
        }

    }

}

public static PaletteController createPalette() {
    try {
        if (null == palette) {
            *//Add null for the PaletteFilter, which we are not using here,
            //and then instantiate your implementation of the DragAndDropHandler*:
            palette = PaletteFactory.createPalette(JAVA_PALETTE_FOLDER, new MyActions(), *null, new MyDragAndDropHandler()*);
        }
        return palette;
    } catch (IOException ex) {
        Exceptions.printStackTrace(ex);
    }
    return null;
}

*//Definition of the DragAndDropHandler:
private static class MyDragAndDropHandler extends DragAndDropHandler {

    MyDragAndDropHandler() {
        super(true);
    }

    //Maybe you don't like the default 'add to palette' implementation,
    //so you could create your own here:
    @Override
    public void customize(ExTransferable t, Lookup item) {
    }

}*