并发问题请教

[goInfall]

public class ThreadDemo {
	public final ExecutorService threadPool = Executors.newCachedThreadPool();
	public final CompletionService<Integer> completionService = new ExecutorCompletionService<Integer>(threadPool);
	public static void main(String[] args) {
		new ThreadDemo().solveCallableList();
	}
	public void solveCallableList() {
		try {
			int sum = 0;
			completionService.submit(new TaskCallable(1));
			completionService.submit(new TaskCallable(2));
			completionService.submit(new TaskCallable(3));
			for (int i = 0; i < 3; i++) {
				int result = completionService.take().get();
				sum += result;
			}
			System.out.println("sum = " + sum);
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	public class TaskCallable implements Callable<Integer> {
		private int options;
		TaskCallable(int options) {
			this.options = options;
		}
		@Override
		public Integer call() throws Exception {
			switch (options) {
			case 1:
				return Integer.valueOf(2 / 0);
			case 2:
				return Integer.valueOf(2 + 1);
			case 3:
				return Integer.valueOf(2 - 1);
			default:
				break;
			}
			return 0;
		}
	}
}

[goInfall]

上面如何获取没有异常的另外两个任务的结果。

[awusoft]

问题呢?凑字数

[goInfall]

这是原来的代码，用了Executors的invokeAll方法，如果其中有一个任务有错误，那么就会抛出异常，但是我还想获得其他的结果值。

public class ThreadDemo {

	public final ExecutorService threadPool = Executors.newCachedThreadPool();
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		new ThreadDemo().solveCallableList();
	}

	public void solveCallableList() {
		try {
			int sum = 0;
			List<Callable<Integer>> callableList = new ArrayList<Callable<Integer>>();
			callableList.add(new TaskCallable(1));
			callableList.add(new TaskCallable(2));
			callableList.add(new TaskCallable(3));
			List<Future<Integer>> futureList = threadPool.invokeAll(callableList, 2000L, TimeUnit.MILLISECONDS);
			if (futureList != null && futureList.size() > 0) {
				for (Future<Integer> future : futureList) {
					int result = future.get();
					sum += result;
				}
			}
			System.out.println("sum = " + sum);
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	public class TaskCallable implements Callable<Integer> {
		private int options;

		TaskCallable(int options) {
			this.options = options;
		}

		@Override
		public Integer call() throws Exception {
			try{
				switch (options) {
				case 1:
					return Integer.valueOf(2 / 0);
				case 2:
					return Integer.valueOf(2 + 1);
				case 3:
					return Integer.valueOf(2 - 1);
				default:
					break;
				}
			}catch(Exception e){
				e.printStackTrace();
			}
			return null;
		}
	}
}

这是改进之后的

public class ThreadDemo1 {
	public final ExecutorService threadPool = Executors.newCachedThreadPool();
	public final CompletionService<Integer> completionService = new ExecutorCompletionService<Integer>(threadPool);

	public static void main(String[] args) {
		new ThreadDemo1().solveCallableList();
	}

	public void solveCallableList() {
		try {
			int sum = 0;
			completionService.submit(new TaskCallable(1));
			completionService.submit(new TaskCallable(2));
			completionService.submit(new TaskCallable(3));
			for (int i = 0; i < 3; i++) {
				int result = completionService.take().get();
				sum += result;
			}
			System.out.println("sum = " + sum);
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	public class TaskCallable implements Callable<Integer> {
		private int options;

		TaskCallable(int options) {
			this.options = options;
		}

		@Override
		public Integer call() throws Exception {
			try {
				switch (options) {
				case 1:
					return Integer.valueOf(2 / 0);
				case 2:
					return Integer.valueOf(2 + 1);
				case 3:
					return Integer.valueOf(2 - 1);
				default:
					break;
				}
			} catch (Exception e) {
				e.printStackTrace();
			}
			return 0;
		}
	}
}

改进之后用ExecutorCompletionService可以获取其他的两个任务的结果值。