The compiler recognizes that "input instanceof ListenableFuture" is
     * impossible. We want the test, though, in case that changes in the future,
     * so we use isInstance instead.
The compiler recognizes that "input instanceof ListenableFuture" is
     * impossible. We want the test, though, in case that changes in the future,
     * so we use isInstance instead. | JdkFutureAdaptersTest.java