《effective java》之九：并发

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第66条：同步访问共享的可变数据：

使用volatile可以在两个线程中通信

public class StopThread {
	private static volatile boolean stopRequested;

	public static void main(String[] args) throws InterruptedException {
		Thread backgroundThread = new Thread(new Runnable() {
			public void run() {
				int i = 0;
				while (!stopRequested)
					i++;
			}
		});
		backgroundThread.start();

		TimeUnit.SECONDS.sleep(1);
		stopRequested = true;
	}
}

 

第67条：避免过度同步：

 千万不要从同步区域内部调用外来方法。尽量限制同步区域内部的工作量。除非迫不得已，否则尽量不要在内部同步类，而是应该让客户在必要的时候从外部同步。

 

第68条：executor和task优先于线程：

 

第69条：并发工具优于wait和notify

 

public class ConcurrentTimer {
	private ConcurrentTimer() {
	} // Noninstantiable

	public static long time(Executor executor, int concurrency,
			final Runnable action) throws InterruptedException {
		final CountDownLatch ready = new CountDownLatch(concurrency);
		final CountDownLatch start = new CountDownLatch(1);
		final CountDownLatch done = new CountDownLatch(concurrency);

		for (int i = 0; i < concurrency; i++) {
			executor.execute(new Runnable() {
				public void run() {
					ready.countDown(); // Tell timer we're ready
					try {
						start.await(); // Wait till peers are ready
						action.run();
					} catch (InterruptedException e) {
						Thread.currentThread().interrupt();
					} finally {
						done.countDown(); // Tell timer we're done
					}
				}
			});
		}

		ready.await(); // Wait for all workers to be ready
		long startNanos = System.nanoTime();
		start.countDown(); // And they're off!
		done.await(); // Wait for all workers to finish
		return System.nanoTime() - startNanos;
	}
}

 

第70条：线程安全性的文档化：

 

第71条：慎用延迟初始化：

 

第72条：不要依赖于线程调度器：

 

第73条：避免使用线程组：

 

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