Absolutely this. See https://google.github.io/guava/releases/23.0/api/docs/src-html/com/google/common/util/concurrent/ListenableFuture.html#line.141 https://goo

Absolutely this. See https://google.github.io/guava/releases/23.0/api/docs/src-html/com/google/common/util/concurrent/ListenableFuture.html#line.141 https://google.github.io/guava/releases/23.0/api/docs/src-ht... For a discussion on some of the dangers of invoking completion listeners synchronously.