File which will have a compile error because of missing log4j.jar in your classpath.

App.java

import org.apache.log4j.Logger;

/**
 * Hello world!
 * 
 */
public class App {
	private static Logger log = Logger.getLogger(App.class);
	@Override
	public String toString() {
		// TODO Auto-generated method stub
		return super.toString();
	}

	public static void main(String[] args) {
		System.out.println("Hello World!");
		log.info("Printed Hello World");
		log.debug("Debug Printed Hello World");
	}
}