多线程，线程锁，实例

多线程可以分多条线程，同时执行程序，但也因此出现一些问题，通过线程锁可以解决
包子实例：
厨师做包子，顾客吃包子，多余50个包子厨师停止做包子，包子为零顾客停止吃包子，当厨师做到10个后顾客可以吃包子
顾客类 Customer.class

public class Customer implements Runnable {
    Pack pack;

    public Customer(Pack pack) {
        this.pack = pack;
    }

    public void run() {
        while (true) {
            synchronized (pack) {
                if (pack.num == 0) {        //包子为0的时候顾客等待并唤醒厨师
                    try {
                        pack.notify();
                        pack.wait();
                    } catch (InterruptedException e) {
                    }
                }
                try {
                    Thread.sleep(200);      //顾客0.2秒吃一个包子（线程睡眠200毫秒）

                } catch (InterruptedException e) {
                }
                pack.num--;
                System.out.println("顾客在吃包子，包子数量：" + pack.num);
            }
        }
    }
}

厨师类 Cooker.class

public class Cooker implements Runnable {
    Pack pack;

    public Cooker(Pack pack) {
        this.pack = pack;
    }

    public void run() {
        while (true) {
            synchronized (pack) {       //增加线程锁，pake是钥匙
                if (pack.num <= 50) {   //包子小于50厨师做包子
                    if (pack.num >= 10) {
                        pack.notify();  //包子大于10个唤醒顾客   
                    }
                    try {
                        Thread.sleep(1000); //1分钟做一个包子（线程睡眠一秒钟）
                    } catch (InterruptedException e) {

                    }
                    pack.num++;
                    System.out.println("厨师在做包子，包子数量：" + pack.num);
                } else {                //多于50个包子，厨师等待
                    try {
                        pack.wait();
                    } catch (InterruptedException e) {
                    }
                }

            }
        }
    }

}

包子类 Pack.class

public class Pack {
    int num;

}

测试类 Test.class

public class Test {
    public static void main(String[] args) {
        Pack pack = new Pack();  //新建包子对象
        pack.num = 50;           //厨师包子数
        //新建线程
        Cooker cook = new Cooker(pack);  
        Thread thread1 = new Thread(cook);

        Customer customer = new Customer(pack);
        Thread thread2 = new Thread(customer);
        //启动线程
        thread1.start();
        thread2.start();
    }

}