Java: What's the reason behind System.out.println() being that slow?

Question

For small logical programs that can be done in a text editor, for tracing I use the classic System.out.println().

I guess you all know how frustrating it is to use that in a block of high number of iterations. Why is it so slow? What's the reason behind it?

Answer 1

This has nothing whatsoever to do with the JVM. Printing text to screen simply involves a lot of work for the OS in drawing the letters and especially scrolling. If you redirect System.out to a file, it will be much faster.

Answer 2

This is very OS-dependent. For example, in Windows, writing to the console is a blocking operation, and it's also slow, and so writing lots of data to the console slows down (or blocks) your application. In unix-type OSes, writing to the console is buffered, so your app can continue unblocked, and the console will catch up as it can.

Answer 3

Ya, there is a huge amount of overhead in writing to the console. Far greater than that required to write to a file or a socket. Also if there are a large number of threads they are all contending on the same lock. I would recommend using something other that System.out.println to trace.