What are the effects of exceptions on performance in Java?

Question

Question: Is exception handling in Java actually slow?

Conventional wisdom, as well as a lot of Google results, says that exceptional logic shouldn\'t be used for n

Answer 1

A while back I wrote a class to test the relative performance of converting strings to ints using two approaches: (1) call Integer.parseInt() and catch the exception, or (2) match the string with a regex and call parseInt() only if the match succeeds. I used the regex in the most efficient way I could (i.e., creating the Pattern and Matcher objects before intering the loop), and I didn't print or save the stacktraces from the exceptions.

For a list of ten thousand strings, if they were all valid numbers the parseInt() approach was four times as fast as the regex approach. But if only 80% of the strings were valid, the regex was twice as fast as parseInt(). And if 20% were valid, meaning the exception was thrown and caught 80% of the time, the regex was about twenty times as fast as parseInt().

I was surprised by the result, considering that the regex approach processes valid strings twice: once for the match and again for parseInt(). But throwing and catching exceptions more than made up for that. This kind of situation isn't likely to occur very often in the real world, but if it does, you definitely should not use the exception-catching technique. But if you're only validating user input or something like that, by all means use the parseInt() approach.