异常捕获

以前使用executor的时候，为了记录任务线程的异常退出会使用ThreadFactory来设置线程的UncaughtExceptionHandler，但是按照书上的验证发现，采用executorService.submit执行任务时，线程抛出的异常并不会被该处理器捕获，而当使用executor.execute提交任务时则会被捕获。代码如下：

final UncaughtExceptionHandler handler = new UncaughtExceptionHandler() {            @Override            public void uncaughtException(final Thread t, final Throwable e) {                System.out.println("uncaught exception");            }        };        ThreadFactory exFactory = new ThreadFactory() {            @Override            public Thread newThread(final Runnable r) {                Thread x = new Thread(r);                x.setUncaughtExceptionHandler(handler);                return x;            }        };        ExecutorService es = Executors.newSingleThreadExecutor(exFactory); 　　　　 // es.execute(new Runnable() {        es.submit(new Runnable() {            @Override            public void run() {                ArrayList
     
       x = new ArrayList
      
       ();                System.out.println(x.get(10)); // index out of bound            }        });
      
     

如果要获得submit任务的异常需要使用其返回的future对象，执行器get方法如下：

ExecutorService es = Executors.newSingleThreadExecutor(exFactory);        Future
     
       f = (Future
      
       ) es.submit(new Runnable() {            @Override            public void run() {                ArrayList
       
         x = new ArrayList
        
         ();                System.out.println(x.get(10));            }        });        try {            f.get();        } catch (InterruptedException e1) {            // TODO Auto-generated catch block            e1.printStackTrace();        } catch (ExecutionException e1) {            // TODO Auto-generated catch block            e1.printStackTrace();        }
        
       
      
     

此时程序会打印错误信息。