Eclipse 3.2 provides extensive support for what is commonly referred to as 'Camel Case' searching, or searching via the capital letter patterns commonly used in naming conventions for classes. This means that if you want to find the class 'ArrayIndexOutOfBoundsException' I can search with 'AIOOBE', or for that matter, any shortened variant of that ('A', 'AI', 'AIO', 'AIOO', etc). Here is an example using the open type dialog (Ctrl+T):

This type of searching goes beyond simply being able to search by capital letters, however; it can also use mixed case to its advantage - for instance, if I had two classes with the 'initials' 'AIOOBE' in my workspace (as you can see in the example above), I can qualify to fewer results by typing something like 'AIOOBExc':

It seems that fewer developers are aware of the fact that this support also works in code assist. So, just like the open-type dialog, if you need to use the ArrayIndexOutOfBoundsException class in your code, you can simply type the capital letters as above, and use the omnipresent Ctrl+Space: