Synchronized use of System.out.println()

Question

So I am again at the point of part of my program running ahead of itself out of the call stack and ruining the sequence or order of printing.
I read that System.out.println() is synchronized so how may it be used to wait() until notified to continue and not ruin the output?

Answer 1

jverd wrote:
Always Learning wrote:
YES SIR EJP! SIR! I thank you for the assistance because using only System.out and synchronizing worked beautifully.You said you're not using multiple threads. If this is true, then there's no reason to synchronize anything. The output will appear on System.out in exactly the order you send it there.
Nos if only I could figure out dependencies to make it work with out and err.You have to stop and think about it for a minute. You know that when you call println() on either one of those two streams, the output may be buffered an not necessarily go immediately to the console. From that you can reason that if you call out.println() first, and then err.println(), that you could end up with err's buffer getting flushed first, and the output appearing on the console in a different order than that in which your code executed the calls.
You are of course not surprised by this, given that you know that out and err are completely independent and just happen to end up at the same destination in this particular case.
So, as a first guess, you might reasonably think that, since buffering is obviously the culprit here, calling flush() on each stream after each print() or println() call should eliminate the problem. In a multithreaded environment, this wouldn't be sufficient, of course, but it's a logical approach to try here.
Another tidbit to make note of is that the System class has setOut() and setErr() calls. Since you're looking at out and err in the same console, you presumably don't care about the distinction between them (which makes me wonder why you're using them both in the first place, instead of just using one). If you're just going to mush them together into the same console anyway, then you can use setOut() or setErr() to make them the same stream, and things will be ordered as you expect.Very interesting Jverd and I think there may yet be life in what I would like to do. I did not know or was not immediately aware of these things. I will give it a try.
To answer your question, I am using them both because, like logging, they are distinct in the Eclipse console (black for out and red for err). With your patch I just tried that distinction has faded but the output is sequenced the same so I do appreciate you noting this. Learn something new in Java each time I am doing a project. I considered using logging and putting errors in a window but I am not sure if I should do that; just not enough experience with it.
Edited by: Always Learning on Oct 23, 2011 9:28 AM