public class Test
{    
    Object o = new Object();
    boolean b = false;
        
    public static void main(String[] args)
    {
        new Thread(new Thread1()).start();
        new Thread(new Thread2()).start();    
    }

    private class Thread1 implements Runnable
    {
        public void run()
        {        
            a();                
        }            
        private void a() throws InterruptedException
        {            
            synchronized(o)
            {
                if(b)
                {
                    wait();
                }
                //执行内容 
            }        
        }        
    }
        
        
    private class Thread2 implements Runnable
    {
        public void run()
        {        
            b();                            
        }
            
        private void b() throws InterruptedException
        {
            b = true;
                
            synchronized(o)
            {
                //执行内容                    
                b = false;
                notify();            
            }
                
        }
    }
}