src/main/java/com/github/oxo42/stateless4j/StateConfiguration.java
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();
            }
        });
    }
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();
            }
        });
    }
Specify an action that will execute when transitioning into the configured state

@param entryAction Action to execute
@return The receiver