Java multithreading errors handling

Question

I have one main thread it has created many workers, every worker is a thread.

How can I get errors from the workers in main thread if there was an Exception in some worker or worker cannot successfully ended ?

How to send error before the worker thread dead ?

Answer 1

If you use the java.util.concurrent Executor frameworks and generate a Future from each submitted worker, then calling get() on the Future will either give you the worker's result, or the exception thrown/caught within that worker.

Answer 2

You can set global UncaughtExceptionHandler which will intercept all uncaught Exceptions in all threads

Thread.setDefaultUncaughtExceptionHandler(new UncaughtExceptionHandler() {
    @Override
    public void uncaughtException(Thread t, Throwable e) {
        ...
    }
});

Answer 3

Use ExecutorService or ThreadPoolExecutor

You can catch Exceptions in three ways

1. Future.get()
2. Wrap entire run() or call() method in try{}catch{}Exceptoion{} blocks
3. Override afterExecute method of ThreadPoolExecutor

Refer to below SE question for more details:

Handling Exceptions for ThreadPoolExecutor