Logger vs. System.out.println

If you are using System.out|err.println(..) to print out user-information on console in your application's main()-method, you do nothing wrong. You can get rid of the message via inserting a comment "//NOPMD".

System.out.println("Fair use of System.out.println(..).");// NOPMD

There is a "Mark as reviewed"-Option in the PMD-Violations Outline for this purpose.

Of course you can trick PMD with following code snippet:

PrintStream out=System.out;
out.println("I am fooling PMD.");  

Outside of your main()-Method use a Log-System like eg Log4j.

UPDATE:

You can also modify the PMD-Rule "SystemPrintln" to use the following XPath:

//MethodDeclaration[@MethodName!="main"]//Name[
starts-with(@Image, 'System.out.print')
or
starts-with(@Image, 'System.err.print')
] | //Initializer//Name[
starts-with(@Image, 'System.out.print')
or
starts-with(@Image, 'System.err.print')
]

This will ignore System.out.println etc in any method named 'main' in your code, but check for System.out.println in initializer code. I like this, because from my point of view, System.out.println is safe in method 'main(String args[])'. But use with caution, I have to check, where in the AST a System.out.println can occur also and have to adapt the XPath.

Loggers has multiple levels for logging.

If we are writing a real short program, just for learning purposes System.out.println is fine but when we are developing a quality software project, we should use professional logger and SOPs should be avoided.

A professional loggers provides different levels for logging and flexibility. We can get the log message accordingly. For example, group X messages should be printed only on PRODUCTION, group Y messages should be printed on ERROR, etc.

We have limited option for redirecting the messages in System.out, but in case of a logger you have appenders which provides numbers of options. We can even create a custom output option and redirect it to that.

See this short introduction to log4j.

The issue is in using System.out to print debugging or diagnostic information. It is a bad practice because you cannot easily change log levels, turn it off, customize it, etc.

However if you are legitimately using System.out to print information to the user, then you can ignore this warning.