My most common mistake in Java is typing StringBugger. The F and G are right next to each other.[Joe's Jelly]
I find I rarely make mistakes like that while coding Java—I use autocomplete for anything longer than three characters anyway. On the other hand, when pair-programming on a Java 1.1 project, and I was dictating code for my pair to type, I used to say things like “enumeration dot nextElephant”to see whether I could get him to type it by mistake.