CompletableFuture<List<Object2LongMap<String>>> (@NotNull List<? extends Path> moduleFiles, @NotNull Executor executor) { return CompletableFuture.supplyAsync(() -> { Object2LongMap<String> result = new Object2LongOpenHashMap<>(moduleFiles.size()); result.defaultReturnValue(-1); addLastModifiedTime(moduleFiles, result); return Collections.singletonList(result); }, executor); }