Question of the Day - Languages and JVM category

How do I get a stack trace in a String?

Wed, 03 Dec 2008 14:32:00 GMT

It comes up every now and then: someone wants a stack trace in a String. They're probably wrong; if they're trying to analyze the stack trace, there are mechanisms in the Throwable to do that without creating a String and parsing it, but just in case... here's how you get a stack trace from an exception in a String.

Filtering characters from a Reader

Thu, 11 Sep 2008 16:25:00 GMT

It's an occasionally legitimate question: "How do I filter content from a Reader?" There're related questions for Streams, too. Here's an example of a simple Reader class that shows how to remove specific characters from a Reader.

How do I parse or format dates? Dates are hard!

Thu, 28 Aug 2008 14:16:00 GMT

Well, Barbie, dates are really pretty easy. Here's a class with a number of formatting and parsing examples.

How can I get all classes in a specific package?

Thu, 28 Aug 2008 11:44:00 GMT

Every so often, we get "How do I get all classes in a specific package?" After all, IDEs do it, right? (You might want to inspect members for, say, a specific interface, or something like that.) There's usually no need to actually do this, but if you're interested, here's how.

I just don't get packages and the classpath!

Wed, 27 Aug 2008 22:58:00 GMT

We hear it about twenty times a day, often (sadly) from the same set of people. Yes, I'm talking about you, _____. The question should take the form of "how does Java use the classpath?" but often looks like "how should I set my classpath" and "how do packages work" and "I'm stupid and my mommy doesn't like me, waaah help with classpath."

Printing a stack trace to a String?

Wed, 27 Aug 2008 15:02:00 GMT

A user on ##java asked "how to printTrackstrace to String," and got an answer of "e.getStackTrace() and concatenate each StackTraceElement." Yeeeick. There not only has to be a better way, but there is a better way.

Is Math.sqrt expensive?

Wed, 27 Aug 2008 13:42:00 GMT

From ##java: "If I was factorising all the numbers up to 1000000, would it be worth checking all primes up to sqrt(n) or would it be quicker to just check all primes up to that number, my tutor told me that the sqrt() function is expensive."