Java 8 introduced default methods in interfaces. This post describes what they are, and how they can change the design of APIs. A nominal design Earlier, in Java, interfaces could only have contracts - method signatures with no implementation. In order to add some implementation, a class was required, whether abstract or not. Hence, traditional API design then followed this hierarchy: The root interface defines the contractAn intermediate class implements common behavior i.e.

As software developers, we behave like children. When we see shiny new things, we just have to play with them. That’s normal, accepted, and in general, even beneficial to our job…​ up to a point. When Java started to provide annotations with version 5, there was a huge move toward using them. Anywhere. Everywhere. Even when it was not a good idea to. But it was new, hence it had to be good. Of course, when something is abused, there’s a strong movement against it.

I’m a regular Spring framework user and I think I know the framework pretty well, but it seems I’m always stumbling upon something useful I didn’t know about. At Devoxx, I learned that you could express conditional dependencies using Java 8’s new Optional type. Note that before Java 8, optional dependencies could be auto-wired using @Autowired(required = false), but then you had to check for null. How good is that?