Add Null checking where applicable

Methods annotated by @NotNull should produce a NullPointerException if invoked by a null argument. As of now, only intent is indicated.

[JerryShea]

If you compile in intellij then it automatically does this instrumentation btw.

My dream is that the compiler can do all this for us i.e. confirm at compile time. There are a few tools I have looked at:

• the combination of NullAway+ErrorProne seems to be reasonably lightweight
• the checkers framework has good support this but adds a bit of time to your compile

Unfortunately both of these work the opposite way to IntelliJ: IntelliJ assumes that everything is nullable unless you explicitly annotate with @NotNull whereas both of these tools assume the opposite. I believe that you can configure the checkers framework to work the same way as Intellij but I have not spent the time.

If we were to follow the compile time static analysis approach on all our products then we could that all our null-related contracts are being respected, although our customers would not get the same assurances for their code.

[minborg]

After some consideration, I agree with you @JerryShea . There are some potentially dangerous corner cases that may be affected by instrumentation. It is better to explicitly use Objects.requireNonNull() where applicable.