I am jealous of Emmanuel (Manu) Stapf who blogged about this before I had the time to; but I can at least refer you to his entry .
The idea actually comes from Martin Nordio, who as part of his thesis work formalized the exception semantics of both Eiffel and Java. In the process he came across some (shall we say) interesting properties of Java, and got into the habit of asking people first if they know Java well, and then if they can predict the results of some simple programs.
So, do you think you know Java? If so, please take the test, and wait for the answer next week in Manu’s blog.
 Emmanuel Stapf: “And people are still using Java?” blog entry.