public static void main(String[] args) {

          AN an= new AN(false);

          Thread t1=new Thread(new Runnable() {

            @Override
            public void run() {

                try {

                    an.Alpha();
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        });


          Thread t2= new Thread(new Runnable() {

            @Override
            public void run() {
                try {
                    an.numbers();
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }

            }
        });


          t1.start();
          t2.start();
}

boolean flag;

AN(boolean flag)
{
    this.flag=flag;
}
synchronized void Alpha() throws InterruptedException
{
    if(flag==false)
    {
    for(char i='A'; i<='Z';i++)
    {
        System.out.println(+i);
        notifyAll();
        flag=true;
    }
    }
    else
    {
        wait();
    }

}

synchronized void numbers() throws InterruptedException
{
    if(flag==true)
    {
    for(int i=1;i<=26;i++)
    {
        System.out.println(+i);
        notifyAll();
        flag=false;
    }
    }
    else
    {
        wait();
    }
}