How to execute a piece of code only after all threads in the threads pool are done?

I want to ensure that all threads created in part1 are executed before executing the code of Part 2.

    @Override
    List<Future<ReconcileResult>> parseAndExecute(ReconcileContext context, File businessReconFile, File bcReconFile) throws Exception {

        List<Future<ReconcileResult>> reconcileResults;
        redisUtil.flushdb();
//PART1
        fileParser.parseAndTransfer(businessReconFile, bcReconFile, executeData -> {
            ThreadUtils.executor.submit(
                    () -> reconcileExecutor.execute_c(context, executeData)
            );
        });
//PART1
//PART2
        reconcileResults = reconcileExecutor.getReconcileResult(context);
//PART2
        return reconcileResults;
    }

One way I came up with is to add "Thread.sleep" between Part1 and part2， But it has great limitations.
Are there any more flexible methods？

>Solution :

I think this thread is helpful:
How to wait for all threads to finish, using ExecutorService?

Based on the above link, there are plenty of ways you can use it. For example, you can call:

List<Future<?>> futures = ThreadUtils.executor.invokeAll(tasks);

or Use cantdownLatch

or call .get() on list of futures (results of your submissions to your executor):

for(Future f: this.futures) { f.get(); }