newFixedThreadPool使用范例：

import java.io.IOException;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

public class Test {

	public static void main(String[] args) throws IOException, InterruptedException {

		ExecutorService service = Executors.newFixedThreadPool(2);

		for (int i = 0; i < 6; i++) {

			final int index = i;

			System.out.println("task: " + (i+1));

			Runnable run = new Runnable() {

				@Override

				public void run() {

					System.out.println("thread start" + index);

					try {

						Thread.sleep(Long.MAX_VALUE);

					} catch (InterruptedException e) {

						e.printStackTrace();

					}

					System.out.println("thread end" + index);

				}

			};

			service.execute(run);

		}

	}

}

从实例可以看到for循环并没有被固定的线程池阻塞住，也就是说所有的线程task都被提交到了ExecutorService中，查看 Executors.newFixedThreadPool()如下：

可以看到task被提交都了LinkedBlockingQueue中。这里有个问题，如果任务列表很大，一定会把内存撑爆，如何解决？看下面：

import java.io.IOException;

import java.util.concurrent.ArrayBlockingQueue;

import java.util.concurrent.BlockingQueue;

import java.util.concurrent.ThreadPoolExecutor;

import java.util.concurrent.TimeUnit;

public class Test {

	public static void main(String[] args) throws IOException, InterruptedException {

		BlockingQueue<Runnable> queue = new ArrayBlockingQueue<Runnable>(3);

		ThreadPoolExecutor executor = new ThreadPoolExecutor(3, 3, 1, TimeUnit.HOURS, queue, new ThreadPoolExecutor.CallerRunsPolicy());

		for (int i = 0; i < 10; i++) {

			final int index = i;

			System.out.println("task: " + (index+1));

			Runnable run = new Runnable() {

				@Override

				public void run() {

					System.out.println("thread start" + (index+1));

					try {

						Thread.sleep(Long.MAX_VALUE);

					} catch (InterruptedException e) {

						e.printStackTrace();

					}

					System.out.println("thread end" + (index+1));

				}

			};

			executor.execute(run);

		}

	}

}

线程池最大值为4（？？这里我不明白为什么是设置值+1，即3+1，而不是3），准备执行的任务队列为3。可以看到for循环先处理4个task，然后把3个放到队列。这样就实现了自动阻塞队列的效果。记得要使用ArrayBlockingQueue这个队列，然后设置容量就OK了。

--heipark