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Thursday, April 02, 2009



This is the most commonly asked question in web applications development in jdeveloper including OA Framework, ADF, ejb, web services etc.

Can I leave System.out.println or System.err.println in the production code?

System.out.println comes handy when debugging the application because you can see the messages pretty much easily in the jdeveloper console. And it takes relatively less time than the debugging option in Jdeveloper. So even experienced developers use it for debugging. You may think, "Anyway this doesnot any affect in the production system". But actually System.out.println statements will have serious performance issue in the production system if you fail to remove them in the final code.

The reason is that the application server will have only one output stream and one error stream in the JVM. Hence multiple threads calling the System.out.println() have to be synchronized.

Considering the production system with thousands of users, back end programs, webservices, scheduled process running parralley in the machine. Calling system.out.println() will potentially block the performance of whole system.

Also the application server doesn't redirect the std out to a file, and is lost.

Hence always remove the System.out.println() /System.err.println() from the production code.

Article By:
Prasanna Jayaraman

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