Java Executor执行器任务提交方式

在Java中，Executor框架提供了一种将任务提交给线程池执行的方式。以下是使用Executor执行器提交任务的几种常见方法：

1. execute(Runnable command): 这是最基本的方法，用于提交不需要返回结果的任务。如果任务执行过程中发生异常，它将被捕获并传递给未捕获异常处理器。

ExecutorService executor = Executors.newFixedThreadPool(4);
executor.execute(new Runnable() {
    @Override
    public void run() {
        System.out.println("Task is running on thread " + Thread.currentThread().getName());
    }
});

2. submit(Callable task): 用于提交需要返回结果的任务。它返回一个Future对象，可以用来检查任务是否完成，并获取任务的返回值。

ExecutorService executor = Executors.newFixedThreadPool(4);
Future<Integer> future = executor.submit(new Callable<Integer>() {
    @Override
    public Integer call() throws Exception {
        System.out.println("Task is running on thread " + Thread.currentThread().getName());
        return 42;
    }
});

try {
    // 获取任务结果，如果任务未完成，get() 方法将阻塞直到完成
    Integer result = future.get();
    System.out.println("Task returned: " + result);
} catch (InterruptedException | ExecutionException e) {
    e.printStackTrace();
}

3. submit(Runnable task, T result): 这个方法允许你在提交任务时指定一个结果，当任务完成时，这个结果将被设置到Future对象中。

ExecutorService executor = Executors.newFixedThreadPool(4);
Future<Integer> future = executor.submit(new Runnable() {
    @Override
    public void run() {
        System.out.println("Task is running on thread " + Thread.currentThread().getName());
    }
}, 42);

try {
    // 获取任务结果，如果任务未完成，get() 方法将阻塞直到完成
    Integer result = future.get();
    System.out.println("Task returned: " + result);
} catch (InterruptedException | ExecutionException e) {
    e.printStackTrace();
}

4. invokeAll(Collection<? extends Callable> tasks): 提交一组任务，并等待所有任务完成。返回一个Future列表，每个Future对应一个任务的执行结果。

ExecutorService executor = Executors.newFixedThreadPool(4);
List<Callable<Integer>> tasks = new ArrayList<>();
tasks.add(new Callable<Integer>() {
    @Override
    public Integer call() throws Exception {
        System.out.println("Task 1 is running on thread " + Thread.currentThread().getName());
        return 42;
    }
});
tasks.add(new Callable<Integer>() {
    @Override
    public Integer call() throws Exception {
        System.out.println("Task 2 is running on thread " + Thread.currentThread().getName());
        return 24;
    }
});

try {
    List<Future<Integer>> futures = executor.invokeAll(tasks);
    for (Future<Integer> future : futures) {
        System.out.println("Task returned: " + future.get());
    }
} catch (InterruptedException | ExecutionException e) {
    e.printStackTrace();
}

5. invokeAny(Collection<? extends Callable> tasks): 提交一组任务，并返回第一个成功完成的任务的结果。如果所有任务都失败，则抛出ExecutionException。

ExecutorService executor = Executors.newFixedThreadPool(4);
List<Callable<Integer>> tasks = new ArrayList<>();
tasks.add(new Callable<Integer>() {
    @Override
    public Integer call() throws Exception {
        System.out.println("Task 1 is running on thread " + Thread.currentThread().getName());
        return 42;
    }
});
tasks.add(new Callable<Integer>() {
    @Override
    public Integer call() throws Exception {
        System.out.println("Task 2 is running on thread " + Thread.currentThread().getName());
        throw new RuntimeException("Task 2 failed");
    }
});

try {
    Integer result = executor.invokeAny(tasks);
    System.out.println("Task returned: " + result);
} catch (InterruptedException | ExecutionException e) {
    e.printStackTrace();
}

在使用完ExecutorService后，应该调用shutdown()或shutdownNow()方法来关闭执行器，以避免资源泄漏。