title: Lightest-weight spacer component in a GridBagLayout
body: <p>In a GridBagLayout, what component is the best for providing empty space in a panel?  Ideally I would like to use a component that has:</p>
  
  <ol>
  <li>Low overhead</li>
  <li>No side effect when no empty space is required (i.e. no minimum size)</li>
  <li>A trivial constructor (no parameters)</li>
  </ol>
  
  <p>A JPanel violates #2 above.  A Box requires a constructor parameter (#3 above), which is really not necessary in this simple case.  A JLabel works well but I worry that it may have some overhead, though admittedly it is probably pretty low.</p>
  
  <p>An anonymous class also seems to work well (i.e. "new JComponent() { }"), but that adds an additional .class file every time I use it.  I suppose it's no more overhead than any given event handler though.  Would it be worth creating a custom, zero-implementation component derived from JComponent for this?  Is there an existing component that I am missing?</p>
  
  <p>FYI GridBagLayout is one of my constraints on the team I'm part of, so other layouts are not an option.</p>