Debugging: to System.out.println() or to not System.out.println()

Question

That is my question. More specifically, I'm trying to get used to Eclipse's debugger and I'd like to know if printing to console is still done in some cases or if it's considered a bad practise that should be entirely avoided. Also, what can be considered as good approach(es) to debugging overall?

Answer 1

Use System.err.println() instead.

Why?

System.out.println() is often redirected to a file or another output, while this is pretty much always printed on the console. It's easier for debugging and also the right way to do it.

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Edit (warning: subjective):

Since you asked about whether System.out.println should be entirely avoided: I don't believe in anything that you must always avoid, be it using goto's, crashing your computer with a BSOD, or whatever. Sometimes you just need a quick-and-dirty way to get small things done fast, and it just plain isn't worth the 1 hour you'll spend on it to try to do things the "right" way, instead of a 5-minute fix, no matter how good the "good" way is. Use your judgment when deciding if something should be used or not, but never set rules for yourself like "I'll never use goto!". :)

Edit 2 (example):

Let's say you're debugging a crashing driver and you suspect that an if statement that shouldn't be execute is being executed. Instead of spending three hours finding out how to use ZwRaiseHardError to display a message box, just call KeBugCheck inside the if and crash the darned system. Sure, you'll reboot, but unless your reboot takes hours, you just saved yourself that much time.