public void registerFuture(long entryIndex, SimpleCompletableFuture future) {
        SimpleCompletableFuture f = futures.put(entryIndex, future);
        assert f == null : "Future object is already registered for entry index: " + entryIndex;
    }
public void registerFuture ( long entryIndex , SimpleCompletableFuture future ) { SimpleCompletableFuture f = futures . put ( entryIndex , future ) ; assert f == null : "Future object is already registered for entry index: " + entryIndex ; }
Registers the future for the appended entry with its {@code entryIndex}.