java 线程交替

public class Num {
    int i=1;
    boolean flag = false; //两个线程，交替执行的一个标志
}

//打印奇数的线程
public class PrintQi implements Runnable{
    Num num ;
    public PrintQi(Num num)
    {
        this.num = num;
    }
    public void run()
    {
        while(num.i<= 100)
        {   
            synchronized (num) {
                if(num.flag)
                {
                    try {
                        num.wait();
                    } catch (Exception e) {
                    }
                }
                else {
                    System.out.println("奇数"+num.i);
                    num.i++;
                    num.flag = true;
                    num.notify();
                }
            }
        }
    }
}

//打印偶数的线程
public class PrintOu implements Runnable{
    Num num;
    public PrintOu(Num num) {
        this.num = num;
    }
    public void run()
    {
        while(num.i<=100)
        {
            synchronized (num)/* 必须要用一把锁对象，这个对象是num*/ {
                if(!num.flag)
                {
                    try 
                    {
                        num.wait();  //操作wait()函数的必须和锁是同一个
                    } catch (Exception e) 
                    {}
                }   
                else {
                    System.out.println("oushu-----"+num.i);
                    num.i++;
                    num.flag = false;
                    num.notify();
                }
            }
        }
    }
}


//主函数
public class main {
    public static void main(String[] args) {
        Num num = new Num(); //声明一个资源

        PrintQi pQi = new PrintQi(num);
        PrintOu pOu = new PrintOu(num);

        Thread aThread = new Thread(pQi);
        Thread bThread = new Thread(pOu);

        aThread.start();
        bThread.start();
    }
}