ExecutorServiceExceptionDemo.java

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

/**
 * Demo of exception handling in ExecutorService.
 */
public class ExecutorServiceExceptionDemo {

    /**
     * A simple job which doesn't handle RuntimeException.
     */
    private static class ExceptionalNumberPrintingJob implements Runnable {
        private final int number;

        public ExceptionalNumberPrintingJob(int num) {
            this.number = num;
        }

        @Override
        public void run() {
            String threadName = Thread.currentThread().getName();

            // randomly trigger a RTE (ArithmeticException in this case)
            if (Math.random() < 0.5) {
                double q = 1 / 0;
            }

            System.out.println(String.format("Thread %s is printing %d.", threadName, number));
        }
    }

    /**
     * Stop new job from being submitted and wait termination.
     * Taken from official documentation:
     * http://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ExecutorService.html
     * @param pool the thread pool
     */
    private static void shutdownAndAwaitTermination(ExecutorService pool) {
        pool.shutdown(); // Disable new tasks from being submitted
        try {
            // Wait a while for existing tasks to terminate
            if (!pool.awaitTermination(60, TimeUnit.SECONDS)) {
                pool.shutdownNow(); // Cancel currently executing tasks
                // Wait a while for tasks to respond to being cancelled
                if (!pool.awaitTermination(60, TimeUnit.SECONDS))
                    System.err.println("Pool did not terminate");
            }
        } catch (InterruptedException ie) {
            // (Re-)Cancel if current thread also interrupted
            pool.shutdownNow();
            // Preserve interrupt status
            Thread.currentThread().interrupt();
        }
    }

    public static void main(String[] args) {
        ExecutorService threadPool = Executors.newFixedThreadPool(2);

        for (int i = 0; i < 10; ++i) {
            threadPool.submit(new ExceptionalNumberPrintingJob(i));
        }

        shutdownAndAwaitTermination(threadPool);
    }
}