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When I was starting study Java, I was being told not to do System.out.println in Java EE application. However I don't really know what is the reason of not doing so.
I am fully aware that if we really need to print an important, it should be logged using logging framework.
What I really want to ask here : is there any real hazard that System.out.println make? Does it cause any performance issue?
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out. println is a Java statement that prints the argument passed, into the System. out which is generally stdout. System is a Class. out is a Variable.
Since System. out. println() is not a field declaration, it's not allowed.
println() is used to print an argument that is passed to it. The statement can be broken into 3 parts which can be understood separately as: System: It is a final class defined in the java. lang package. out: This is an instance of PrintStream type, which is a public and static member field of the System class.
It's indeed a performance issue. If you dig down into the JDK source code for System.out you'll eventually encounter a synchronized block on the output stream.
That means that if you put enough println calls in your source code, the entire code base will effectively run single-threaded, because all threads are waiting for the synchronization lock.
There are some statistics involved here, a single call to println generally isn't going to bring your entire application to a crawl. The more println calls in your code, the more likely two or more threads will have to wait for eachother.
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