Are you still with us? If so, congratulations. We started with some of the basic Java functions, such as methods, and then moved on to understand advanced Java functions. That's some complicated stuff we just went over. As you become a more experienced programmer, you'll begin to internalize concepts such as these and you won't have to really think about them explicitly when you're writing day-to-day code. For now, though, there's some logic shortcuts we can use to keep from getting too tripped up.
In the next chapter, you will learn about modeling using object-oriented Java programs in detail.