The standard Java class MessageDigest can be used to return instances for various message digest algorithms. Implementing a simple factory helps you to return these instances in a type safe way without magic strings and preventing catch blocks with NoSuchAlgorithmException in your code.
An interesting piece worth sharing are two apparent easter eggs that can be found in the Google search: type in recursion or answer to life the universe and everything and see what happens. Apparently, there are more like these but I like them the most.
Generally it’s frustrating to read that somebody implemented the Steinhaus–Johnson–Trotter algorithm to generate permutations but doesn’t supply the source code due to the fear that the code could be “copied elsewhere” on the internet. Since I was really interested in permutations for another project I implemented the said algorithm, added a LGPL license to it …
If you’re using the qTranslate plugin for WordPress and want to insert the Facebook Like button in the corresponding language I came up with a small piece of code that you can insert into, e.g., your theme’s functions.php to get this working.