Why use Log4j logging vs System.out.println in Java

Printing messages to the console is an integral part of development, testing and debugging a Java program. If you are working on a Server side application, where you can not see what's going on inside the server, your only visibility tool is a log file; without logs, you can not do any debugging or see what's going on inside your application. Though, Java has pretty handy System.out.println() methods to print something on console, which can also be routed to log file but not sufficient for a real-world Java application. If you are running a Java program in Linux or any UNIX based system, Log4j or SLF4j or any other logging framework offers a lot more features, flexibility, and improvement on message quality, which is not possible using the System.out.println() statement.

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