How to use @Nullable and @Nonnull annotations more effectively?

Question

I can see that @Nullable and @Nonnull annotations could be helpful in preventing NullPointerExceptions but they do not propag

Answer 1

Short answer: I guess these annotations are only useful for your IDE to warn you of potentially null pointer errors.

As said in the "Clean Code" book, you should check your public method's parameters and also avoid checking invariants.

Another good tip is never returning null values, but using Null Object Pattern instead.