Design patterns are these cool things that make you go 'hell yeah' because they make a certain problem easier to deal with. Whether it's applicable to all languages, or due to a language constraint, they're pretty nice. Of course, some people go crazy with them rather than doing the simple thing that works. Other times, you'll naturally do a design pattern without even knowing about it...

In the recent years, reactive Java has been growing in popularity, but writing reactive code is tricky to get used to due to the asynchronous (non-blocking) style it requires. Furthermore, asynchronous Java comes with some common pains..