Eugene Kuleshov has been using ASM to take a peek at the bytecode in rt.jar to learn what is going on. His first statistics charted the various opcodes used in the runtime.
Then he looked at exceptions, and charted the number of checked exceptions that methods in the runtime have. One of them declares eleven!
The good news is that the majority declare 0 or 1.
Is there anything that you would like to know?
Read: Some statistics on Java bytecode: Exceptions
, and Some statistics on Java bytecode: op codes