线程同步出错的

采用信号量和同步方法使得发送线程和接收线程同步运行
public class BufferLock {
private int value;
private boolean isEmpty=true;
public synchronized void put(int i)
{
    while(!isEmpty)
        try
    {
            this.wait();
    }
    catch(InterruptedException e){}
    value=i;
    isEmpty=false;
    notify();
}
public synchronized int get()
{
    while(isEmpty)
        try
    {
            this.wait();
    }
    catch(InterruptedException e){}
    isEmpty=true;
    notify();
    return value;
}
}

class Sender extends Thread
{
    private BufferLock buffer;
    public Sender(BufferLock buffer)
    {
        this.buffer=buffer;
    }
    public void run()
    {
        for(int i=1;i<6;i++)
        {
            buffer.put(i);
            System.out.println("Send put:"+i);
        }
    }
   
}

class Receiver extends Thread
{
    private BufferLock buffer;
    public Receiver(BufferLock buffer)
    {
        this.buffer=buffer;
        
    }
    public void run()
    {
        for(int i=1;i<6;i++)
        {
            System.out.println("\t\t\tReceiver get:"+buffer.get());
        }
    }
        public static void main(String args[])
        {
            BufferLock buffer=new BufferLock();
            (new Sender(buffer)).start();
            (new Receiver(buffer)).start();
        }
    }


但是最后运行的结果还是随机的，总是不能同步，到底是什么原因想不明白
ps：程序是书上的，用的是 eclipse[local]1[/local]