code: public void add(final Class<?> clazz) {
  		if (this.clazzes.contains(clazz)) {
  			throw new IllegalArgumentException(
  					"Only one class-instance per benchmark allowed");
  		} else {
  			this.clazzes.add(clazz);
  		}
  	}
docs: Adding a class to bench to this benchmark. This class should contain
  benchmarkable methods, otherwise it will be ignored.
  
  @param clazz
  to be added.