Java7新特性（四）并发 7 ScheduledThreadPool

本文主要根据《Java程序员修炼之道》整理的代码笔记片段

工作单元

public class WorkUnit<T> {
  private final T workUnit;

  public T getWork() {
    return workUnit;
  }

  public WorkUnit(T _workUnit) {
	  workUnit = _workUnit;
  }
}

计划线程池（启动、关闭、执行队列中工作单元）

public class ScheduledThreadPoolExecutorClass {
	private ScheduledExecutorService stpe;
	private ScheduledFuture<?> hndl;
	
	BlockingQueue<WorkUnit<String>> lbq =
			new LinkedBlockingQueue<>();
			
	private void run(){
		stpe = Executors.newScheduledThreadPool(2);
		
		final Runnable msgReader = new Runnable() {
			
			@Override
			public void run() {
				String nextMsg = lbq.poll().getWork();
				if(nextMsg != null){
					System.out.println("Msg recvd: "+ nextMsg);
				}
			}
		};
		
		hndl =stpe.scheduleAtFixedRate(msgReader, 10, 10, TimeUnit.MILLISECONDS);
	}
	
	private void cancel(){
		final ScheduledFuture<?> myHndl = hndl;
		
		stpe.schedule(new Runnable() {			
			@Override
			public void run() {
				myHndl.cancel(true);
			}
		}, 10, TimeUnit.MILLISECONDS);
	}
	
	public static void main(String[] args) {	
		ScheduledThreadPoolExecutorClass s = new ScheduledThreadPoolExecutorClass();
		for (int i = 0; i < 10; i++) {
			s.lbq.add(new WorkUnit<String>(i+""));
		}		
		s.run();
		for (int i = 10; i < 20; i++) {
			s.lbq.add(new WorkUnit<String>(i+""));
		}	
		
	}
}

think in java 实例 Callable

/*
	The submit( ) method produces a Future object, 
parameterized for the particular type of result 
returned by the Callable. You can query the 
Future with isDone( ) to see if it has completed. 
When the task is completed and has a result, 
you can call get( ) to fetch the result. 
You can simply call get( ) without checking isDone( ),
in which case get( ) will block until the result is ready. 
You can also call get( ) with a timeout, 
or isDone( ) to see if the task has completed,
before trying to call get( ) to fetch the result.
	
	The overloaded Executors.callable( ) method 
takes a Runnable and produces a Callable. 
ExecutorService has some "invoke" methods 
that run collections of Callable objects.
*/


public class CallableDemo {
	public static void main(String[] args) {
		ExecutorService exec = Executors.newCachedThreadPool();
		ArrayList<Future<String>> results = new ArrayList<Future<String>>();
		for (int i = 0; i < 10; i++)
			results.add(exec.submit(new TaskWithResult(i)));
		for (Future<String> fs : results)
			try {
				// get() blocks until completion:
				System.out.println(fs.get());
			} catch (InterruptedException e) {
				System.out.println(e);
				return;
			} catch (ExecutionException e) {
				System.out.println(e);
			} finally {
				exec.shutdown();
			}
	}
}

class TaskWithResult implements Callable<String> {
	private int id;

	public TaskWithResult(int id) {
		this.id = id;
	}

	public String call() {
		return "result of TaskWithResult " + id;
	}
}