Let's check out some Java Cryptography, considering both symmetric and asymmetric algorithms.
Let's use reflection to set a bunch of configurable values via the command-line using "system properties."
The "Google Operating System" blog entry "Google Docs & Spreadsheets vs Microsoft Office" quotes a Writely post as follows.
Passwords should never be seen in clear text eg. in transfer objects, or in database columns. So we hash them up. Nothing to it.
We implement a event listener list singleton supporting weak references.
Then we can add listeners to an object we wish to observe, and fire events to its observers, without implementing any such support in the observed objects eg. addListener(), removeListener(), fireEvent().
In the Gooey Beans Info prequel, we explicitly declare properties. Now we allow a bean info instance to be bound to a specific bean, in order to support bound properties ie. firing PropertyChangeEvent's.
Having defined style objects in the Hyper Style prequel, we build an "HTML builder" to generate HTML/CSS.
Do you use Google Reader? But why not?! ;)