code: public StateConfiguration<S, T> onEntry(final Action entryAction) {
          assert entryAction != null : ENTRY_ACTION_IS_NULL;
          return onEntry(new Action1<Transition<S, T>>() {
              @Override
              public void doIt(Transition<S, T> t) {
                  entryAction.doIt();
              }
          });
      }
docs: Specify an action that will execute when transitioning into the configured state
  
  @param entryAction Action to execute
  @return The receiver