[Java] Using Log4j in Eclipse

Step by step:

1. Get Log4j: Download Apache log4j from http://logging.apache.org/log4j/. Apache log4j has three development branches: a stable branch, 1.2; a discontinued branch, 1.3; and an experimental branch, 2.0.
   
   
2. Setup: Unzip the file in the dedicated directory. log4j-x.y.z.jar should be in log4j directory.
   
   
3. Use Log4j: There are two examples in log4j directory:
   
   • Trivial.java for a trivial usage example.
     
   • Sort.java and SortAlgo.java to for a slightly more advanced example.
   We take Trivial.java for example. First create a new project. Then add log4j-x.y.z.jar into libraries:

   Right click the project in Package Explorer. Then click Properties > Java Build Path > Libraries > Add External JARs...

   Now we add Main.java and Trivial.java classes: In Main.java:

   public class Main {
       public static void main(String[] args) {
           Trivial.run(args);
       }
   }

   In Trivial.java, we change main() method's name to run(). Run:
   
   Trivial class should output four lines.

Enjoy!