class LN

{

    private int flag = 0;

    public static char ch = 'A';

    public static int n = 1;

    public synchronized void printLetter()

    {

        try

        {

            if(flag == 0 || flag == 1)

            {

                wait();

            }

            else

            {

                //System.out.println("flag = " +     flag);

                System.out.print(ch);

                ch++;

                flag = (flag + 1) % 3;

                notifyAll();

            }

        }

        catch(InterruptedException ex)

        {

            ex.printStackTrace();

        }

    }

    public synchronized void printNumber()

    {

        try

        {

            if(flag == 2 )

            {

                wait();

            }

            else

            {

                //System.out.println("flag = " +     flag);

                System.out.print(n);

                n++;        

                flag = (flag + 1) % 3;

                notifyAll();

            }

        }

        catch(InterruptedException ex)

        {

            ex.printStackTrace();

        }

    }

}

class Letter extends Thread

{

    LN ln;

    Letter(LN ln)

    {

        this.ln = ln;

    }

    public void run()

    {

        for(int i = 0 ; i< 26; i++)

        {

            ln.printLetter();

        }

    }

}

class Number extends Thread

{

    LN ln;

    Number(LN ln)

    {

        this.ln = ln;

    }

    public void run()

    {

        for(int i = 0 ; i< 78; i++)

        {

            ln.printNumber();

        }

    }

}

class Practice1

{

    public static void main(String[] args) {

        LN ln = new LN();

        new Letter(ln).start();

        new Number(ln).start();

    }

}

public class ThreadDemo {

// 测试

public static void main(String[] args) {

Object obj = new Object();

// 启动两个线程

Thread1 t1 = new Thread1(obj);

Thread2 t2 = new Thread2(obj);

t1.start();

t2.start();

}

}

class Thread1 extends Thread {

private Object obj;

public Thread1(Object obj) {

this.obj = obj;

}

public void run() {

// 加锁

synchronized (obj) {

// 打印1-52

for (int i = 1; i < 53; i++) {

System.out.print(i);

if (i % 2 == 0) {

// 不能忘了唤醒其它线程

obj.notifyAll();

try {

obj.wait();

} catch (InterruptedException e) {

e.printStackTrace();

}

}

}

}

}

}

class Thread2 extends Thread {

private Object obj;

public Thread2(Object obj) {

this.obj = obj;

}

public void run() {

synchronized (obj) {

// 打印A-Z

for (int i = 0; i < 26; i++) {

System.out.print((char) ('A' + i));

// 不能忘了唤醒其它线程

obj.notifyAll();

try {

obj.wait();

} catch (InterruptedException e) {

e.printStackTrace();

}

}

}

}

}