Force not null

Having the freedom to return null is the root cause for most NullPointerExceptions. It also makes the client code for any API or method etc dirty by having a lot of null checks.

Solution

• If you feel the need for a null while using your own code (i.e. excluding external libraries). Rethink the implementation of that part to not return null
• Force IDE/Compiler to not allow returning null. It will complain whenever you return or pass in a value that is null or can be null https://github.com/osundblad/intellij-annotations-instrumenter-maven-plugin
• It boosts developer's confidence by not worrying about NPE while coding.
• For exceptional cases where you really need that null you can use the @Nullable annotation, it also makes it clear to other developers that there could be a null value which they should handle.