// 从list中读数据
    public static class ReadThread implements Runnable {

        @Override
        public void run() {
            System.out.println("start read size: " + list.size() + " thread : " + Thread.currentThread().getName());
            for (UUID uuid : list) {
                System.out.println("Read uuid : " + uuid + " size : " + list.size() + "thread: " + Thread.currentThread().getName());
            }
        }
    }

    public static void main(String[] args) throws InterruptedException {
        initThread(new AddThread(), 10);
        initThread(new ReadThread(), 100);
    }

    private static void initThread(Runnable runnable, int maxNum) throws InterruptedException {
        Thread[] ts = new Thread[maxNum];
        for (int k = 0; k < maxNum; k++) {
            ts[k] = new Thread(runnable);
        }
        for (int k = 0; k < maxNum; k++) {
            ts[k].start();
        }
    }
}

下图运行结果中可以看出来, 同一个线程, 即使在读的过程中发生了size变化, 也不会抛出ConcurrentModificationException