小编典典

定义一个回调接口，以接收要在完成通知中传递的任何参数。然后在任务结束时调用它。

你甚至可以为Runnable任务编写通用包装，并将其提交给ExecutorService。或者，请参阅下面的Java 8中内置的机制。

class CallbackTask implements Runnable {

private final Runnable task;

private final Callback callback;

CallbackTask(Runnable task, Callback callback) {

this.task = task;

this.callback = callback;

}

public void run() {

task.run();

callback.complete();

}

}

使用CompletableFutureJava 8，Java 8包含了一种更精细的方法来组成管道，在该管道中可以异步和有条件地完成进程。这是一个人为但完整的通知示例。

import java.util.concurrent.CompletableFuture;

import java.util.concurrent.ThreadLocalRandom;

import java.util.concurrent.TimeUnit;

public class GetTaskNotificationWithoutBlocking {

public static void main(String... argv) throws Exception {

ExampleService svc = new ExampleService();

GetTaskNotificationWithoutBlocking listener = new GetTaskNotificationWithoutBlocking();

CompletableFuture f = CompletableFuture.supplyAsync(svc::work);

f.thenAccept(listener::notify);

System.out.println("Exiting main()");

}

void notify(String msg) {

System.out.println("Received message: " + msg);

}

}

class ExampleService {

String work() {

sleep(7000, TimeUnit.MILLISECONDS); /* Pretend to be busy... */

char[] str = new char[5];

ThreadLocalRandom current = ThreadLocalRandom.current();

for (int idx = 0; idx < str.length; ++idx)

str[idx] = (char) ('A' + current.nextInt(26));

String msg = new String(str);

System.out.println("Generated message: " + msg);

return msg;

}

public static void sleep(long average, TimeUnit unit) {

String name = Thread.currentThread().getName();

long timeout = Math.min(exponential(average), Math.multiplyExact(10, average));

System.out.printf("%s sleeping %d %s...%n", name, timeout, unit);

try {

unit.sleep(timeout);

System.out.println(name + " awoke.");

} catch (InterruptedException abort) {

Thread.currentThread().interrupt();

System.out.println(name + " interrupted.");

}

}

public static long exponential(long avg) {

return (long) (avg * -Math.log(1 - ThreadLocalRandom.current().nextDouble()));

}

}

2020-03-09