AsyncCallableReturnsNull
AsyncCallable should not return a null Future, only a Future whose result is null.

Severity
ERROR
Has Fix?
NO_FIX

The problem

Methods like Futures.whenAllComplete(…).callAsync(…) will throw a NullPointerException if the provided AsyncCallable returns a null Future. To produce a Future with an output of null, instead return immediateFuture(null).

Suppression

Suppress false positives by adding the suppression annotation @SuppressWarnings("AsyncCallableReturnsNull") to the enclosing element.