code: public void addJar(Path jar) {
  		if (jar == null) {
  			throw new IllegalArgumentException();
  		}
  
  		if (!userJars.contains(jar)) {
  			userJars.add(jar);
  		}
  	}
docs: Adds the path of a JAR file required to run the job on a task manager.
  
  @param jar
  path of the JAR file required to run the job on a task manager