How to re-throw an exception to catch-block in another thread

Question

I've code that looks like this:

public static void startService() {
            try{
            new Thread(new Runnable() {
                @Override
                public void run() {
                    throw new RuntimeException("Some exception");
                }
            }).start();
            }catch (Exception e){
                //Exception handling
            }
        }

How can I handle this exception in the catch() block in parrent thread? UPD : This threads have to work asynchronous

Answer 1

You have several options to handle exceptions thrown by threads. One is to have a general uncaught exceptions handler:

Thread.setDefaultUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() {
    @Override
    public void uncaughtException(Thread t, Throwable e) {
        //log the exception or handle it here if possible
    }
});

But it is difficult to link an exception caught that way with a specific thread.

Or you can use an ExecutorService instead of starting the thread manually:

ExecutorService executor = Executors.newCachedThreadPool();
Future<?> future = executor.submit(new Runnable() {
    @Override
    public void run() {
        throw new RuntimeException("Some exception");
    }
});

try {
   future.get();
} catch (ExecutionException e) {
    Throwable yourException = e.getCause(); //here you can access the exception
}

Answer 2

抛出异常只是在catch块中添加throw e

Answer 3

If you mean it is inside of Runnable's run() method then you will have to use another approach. Use Callable instead! Callable call() method allows you to return a value and throw an exception.

Please have a look here for an example on how to use Callable . Also, note that it is better to use a higher level api such as ExecutorService which manages the lifecycle of your threads and provides thread pooling. (included in the example)

Answer 4

you would have to use an Callable.

The thread.run method will never throw an exception since it is - well - executed in a different thread and in this was will not interfere with your calling thread.

if you execute a callable (by eg running it via an ExecutorService) you get a Future result which in turn will throw the given exception when calling the future.get() method.

Answer 5

Use throw statement in catch block.

public static void startService() {
        try{
        new Thread(new Runnable() {
            @Override
            public void run() {

            }
        }).start();
        }catch (Exception e){
            throw e;
    }
}