Methods that return
java.util.concurrent.Future and its subclasses generally
indicate errors by returning a future that eventually fails.
If you don’t check the return value of these methods, you will never find out if they threw an exception.
Nested futures can also result in missed cancellation signals or suppressed exceptions - see Avoiding Nested Futures for details.
Suppress false positives by adding the suppression annotation
@SuppressWarnings("FutureReturnValueIgnored") to the enclosing element.