public class TestLock {
    final ReentrantLock reentrantLock = new ReentrantLock(true);
    private static int number;

    void test(){
        try {
            reentrantLock.lock();
            number++;
            System.out.println(Thread.currentThread().getName()+"    finished_"+number);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            reentrantLock.unlock();
        }

    }
}

public class ThreadLock extends Thread{


    private final Object object = new TestLock();

    public ThreadLock(String threadName){
        super(threadName);
    }
    public void run() {
        if(object instanceof TestLock){
            ((TestLock) object).test();
        }
    }

    public static void main(String[] args) {
        Thread thread1 = new ThreadLock("thread1");
        Thread thread2 = new ThreadLock("thread2");
        Thread thread3 = new ThreadLock("thread3");
        Thread thread4 = new ThreadLock("thread4");
        Thread thread5 = new ThreadLock("thread5");
        thread1.start();
        thread2.start();
        thread3.start();
        thread4.start();
        thread5.start();
    }
}

结果竟然出现了重复数据：

"C:\Program Files\Java\jdk1.8.0_112\bin\java"
thread1    finished_2
thread2    finished_2
thread3    finished_3
thread5    finished_4
thread4    finished_4

Process finished with exit code 0

请问各位大神这是为什么？