This week's book giveaway is in the Mac OS forum. We're giving away four copies of a choice of "Take Control of Upgrading to Yosemite" or "Take Control of Automating Your Mac" and have Joe Kissell on-line! See this thread for details.
A HashMap is frequently used when you want to associate data of some kind (must be an object) with a specific key. A lookup of the keyed data is as simple as a single get() call on the hash map instance. The key can be any object, although Strings are frequently used. Be aware that to use an object of your own class as the key, you must be diligent about over-riding hashMap() and equals() from the Object class (anyone else know of any other potential pitfalls?) What did you have in mind for its use? hth, bear