Lightest-weight spacer component in a GridBagLayout

Question

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:

1. Low overhead
2. No side effect when no empty space is required (i.e. no minimum size)
3. A trivial constructor (no parameters)

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.

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?

FYI GridBagLayout is one of my constraints on the team I'm part of, so other layouts are not an option.

Answer 1

You mention Box but it can be used in a "lightweight" fashion with the following four static methods that simply return a component. I use these all the time. They're invisible with respect to painting. In your case it looks like the glues are the way to go. A trivial constructor (like that's a bad thing!), low overhead. The side-effect when no space is required is all down to how you layout your gridbag.

panel.add( Box.createHorizontalGlue() );
panel.add( Box.createVerticalGlue() );
panel.add( Box.createHorizontalStrut( int width ) );
panel.add( Box.createVerticalStrut( int width ) );

JavaDoc here: http://java.sun.com/javase/6/docs/api/javax/swing/Box.html