One way to correct this problem is to implement an empty Icon having the desired size, but whose paintIcon method does nothing. For menu items without an icon, adding an empty Icon will simply move the text over the desired amount.

Example

package hirondelle.stocks.util.ui;

import javax.swing.Icon;
import java.awt.Component;
import java.awt.Graphics;
import hirondelle.stocks.util.Args;

/**
* Represents a square icon having no graphical content.
*
* <P>Intended for use with <tt>Action</tt> and <tt>JMenuItem</tt>. 
* Alignment of text is poor when the same menu mixes menu items without an icon with 
* menu items having an icon. In such cases, items without an icon can use 
* an <tt>EmptyIcon</tt> to take up the proper amount of space, and allow 
* for alignment of all text in the menu.
*/
final class EmptyIcon implements Icon {

  /**
  * Convenience object for small icons, whose size matches the size of 
  * small icons in Sun's graphics repository.
  */
  static final EmptyIcon SIZE_16 = new EmptyIcon(16);

  /**
  * Convenience object for large icons, whose size matches the size of 
  * large icons in Sun's graphics repository.
  */
  static final EmptyIcon SIZE_24 = new EmptyIcon(24);
  
  /**
  * EmptyIcon objects are always square, having identical height and width.
  *
  * @param aSize length of any side of the icon in pixels, must 
  * be in the range 1..100 (inclusive).
  */
  EmptyIcon(int aSize) {
    Args.checkForRange(aSize, 1, 100);
    fSize = aSize;
  }

  /**
  * Return the icon size (width is same as height).
  */
  @Override public int getIconWidth() {
    return fSize;
  }

  /**
  * Return the icon size (width is same as height).
  */
  @Override public int getIconHeight() {
    return fSize;
  }

  /**
  * This implementation is empty, and paints nothing.
  */
  @Override public void paintIcon(Component c, Graphics g, int x, int y) {
    //empty
  }

  // PRIVATE
  private int fSize;
}