Wednesday, February 04, 2009 4:19 PM | rahel luethy | 1 comment(s)

generified

one of the java language features which i personally discovered quite late and use only very rarely, but which maybe still is a good addition to any developer's toolbox: the possibility to specify multiple bounds for a type parameter via the T extends T1 & T2 ... & Tn syntax.

a simple example:

abstract class GenericDialog<T extends JPanel & Disposable> ... { private final T panel; public GenericDialog(Window owner, String title) { super(owner, title); panel = createPanel(); addWindowListener(new WindowAdapter() { @Override public void windowClosing(WindowEvent e) { panel.dispose(); } @Override public void windowClosed(WindowEvent e) { panel.dispose(); } }); getContentPane().add(panel, BorderLayout.CENTER); } public abstract T createPanel(); }

instead of typing the dialog to e.g. a DisposablePanel class, we use multiple bounds to combine the two roles dynamically (and thus keep the class hierarchy cleaner).

2:16 PM |  David Moles said...

Note that it doesn't always do as much as it ought to, though.