线程与线程池，实例比较。

线程池：

int count = 200000;
        long startTime = System.currentTimeMillis();
        final List<Integer> l = new LinkedList<Integer>();
        ThreadPoolExecutor tp = new ThreadPoolExecutor(1, 1, 60, TimeUnit.SECONDS, new LinkedBlockingDeque<Runnable>(count));
        final Random random = new Random();
        for (int i = 0; i < count; i++) {
            tp.execute(new Runnable() {

                @Override
                public void run() {
                    l.add(random.nextInt());
                }
            });
        }
        tp.shutdown();
        try {
            tp.awaitTermination(1, TimeUnit.DAYS);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(System.currentTimeMillis() - startTime);
        System.out.println(l.size());

输出结果：

1 172
2 200000

线程：

int count = 200000;
        long startTime = System.currentTimeMillis();
        final List<Integer> l = new LinkedList<Integer>();
        final Random random = new Random();
        for (int i = 0; i < count; i++) {
            Thread thread = new Thread(){
                @Override
                public void run(){
                    l.add(random.nextInt());
                }
            };
            thread.start();
            try {
                thread.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        System.out.println(System.currentTimeMillis() - startTime);
        System.out.println(l.size());

输出结果：

1 33556
2 200000

总结：差异在于线程池是复用线程的，而不使用线程池是每次都要去创建线程。线程中执行工作很简单，创建线程的开销占整个时间的比例较大。

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