java中关于线程间协作所用关键字synchronized，wait,notify的用法

package thread_waitnotify;

public class ProductFactory {
    class Worker implements Runnable {
        private final Object lockObject = new Object();
        private volatile boolean hasWork = false;

        private void waitTakeTask() {
            synchronized (lockObject) {
                while (!hasWork) {
                    try {
                        System.out.println("等待中...");
                        lockObject.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
                takeTask();
            }
        }

        private void takeTask() {
            boolean tmpHasWork = false;
            synchronized (lockObject) {
                if (hasWork)
                    tmpHasWork = true;
            }
            if (tmpHasWork) {
                System.out.println("开始做任务...");
                try {
                    Thread.sleep(3000);
                    synchronized (lockObject) {
                        hasWork = false;
                    }
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

                System.out.println("任务完成，休息3s后退出...");
                try {
                    Thread.sleep(3000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

                // System.out.println("任务完成，继续寻找下一项任务...");
                // takeTask();
            } else {
                System.out.println("暂时没有任务，进入等待状态...");
                waitTakeTask();
            }
        }

        public void notifyChange() {
            synchronized (lockObject) {
                hasWork = true;
                System.out.println("起床开工了...");
                lockObject.notifyAll();// 唤醒所有等待获取lockObject锁的线程
            }
        }

        @Override
        public void run() {
            takeTask();
        }
    }

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

        Worker worker = new ProductFactory().new Worker();
        Thread thread = new Thread(worker);
        thread.start();
        Thread.sleep(3000);// 主线程休眠3s后唤醒子线程
        worker.notifyChange();// 主线程设置子线程中的信号量并唤醒阻塞的线程

        thread.join();// 主线程阻塞，等待子线程执行完成后继续主线程的执行
        System.out.println("子线程执行完成,主线程退出。");
        System.exit(0);
    }

}