线程安全 Vs 非线程安全

线程安全：多线程访问时，采用了加锁机制，当一个线程读取数据时，其他线程不能访问直到该线程读取完毕。不会出现数据不一致或者脏数据。

非线程安全：不提供数据保护，可能出现其他线程访问时更改数据而该线程得到脏数据。

线程安全	非线程安全
Vector	ArrayList
HashTable	HashMap
StringBuffer	StringBuilder

public class Thread_Demo2 {

    public static void main(String[] args) {
        Test();
    }

    public static void Test() {
        //List<Object> list = new Vector<Object>();
        List<Object> list = new ArrayList<Object>();
        int threadcount = 1000;
        CountDownLatch countDownLatch = new CountDownLatch(threadcount);
        for (int i = 0; i < threadcount; i++) {
            Thread thread = new Thread(new MyListThread(list, countDownLatch));
            thread.start();
        }

        try {
            countDownLatch.await();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        System.out.println(list.size());

    }
}

class MyListThread implements Runnable {
    private List<Object> list;
    private CountDownLatch countDownLatch;

    public MyListThread(List<Object> list, CountDownLatch countDownLatch) {
        this.list = list;
        this.countDownLatch = countDownLatch;
    }

    @Override
    public void run() {
        for (int i = 0; i < 100; i++) {
            list.add(new Object());
        }
        countDownLatch.countDown();
    }

}

 使用ArrayList发起100*1000线程，得到的结果是99738.

使用Vector