code: private void handleArgInputHandler(final Deque<String> args) {
          if (inputHandlerClassname != null) {
              throw new BuildException("Only one input handler class may be specified.");
          }
          inputHandlerClassname = args.pop();
          if (inputHandlerClassname == null) {
              throw new BuildException("You must specify a classname when using the --inputhandler" + " argument");
          }
      }
docs: Handle the --inputhandler argument.