求教读者与写者问题

[baar]

正在做一个读者写者问题的作业，要求读者写者公平竞争，我用了队列模拟FIFO的已达到公平竞争，但是在运行时候一直提示队列为空，查了好久，发现我的endReading和endWriting方法在读写完之后均无调用，请问是什么原因？谢谢
下面是我写的程序

这个类是共用堆

import java.util.Queue;


public class Puffer {
	private int readerCount;//读者数
	 private int writerCount;//写者数
	 private boolean dbReading;//读信号量
	 private boolean dbWriting;//写信号量
	 private Queue queue;
	 
	 public Puffer() {
	  readerCount=0;
	  writerCount=0;
	  dbReading=false;
	  dbWriting=false;
	 
	 }
	 public synchronized int startRead(Reader r){//开始读
	  while(writerCount>0){
	   try{
		queue.add(r);
	    System.out.println("reader is waiting");
	    wait();//等待写者发出notify
	   }
	   catch(Exception e){
	   }
	  }
	  readerCount++;
	  if(readerCount==1){
	  dbReading=true;
	  }
	  return readerCount;
	 }
	 
	 public synchronized int endReading(){//结束读
	  --readerCount;
	  System.out.println("endReading"+queue.size());
	  
	  if(readerCount==0&&queue.size()!=0){
		  dbReading=false;
		 
		  for(Object o:queue)
		  {
			  
			  if(o.toString().equals("Reader"))
			  {
				  notifyAll();
				  queue.remove();
			  }else
			  {
				  notifyAll();
				  break;
			  }
		  }//没有读者
	   
	  }
	
	  //notifyAll();
	  System.out.println("one reader is done reading. readerCount="+readerCount);
	  return readerCount;
	 }
	 public synchronized void startWriting(Writer w){//开始写
		  ++writerCount;
		  while(dbReading==true||dbWriting==true){
		   try{
			queue.add(w);
		    System.out.println("Writer "+writerCount+" is waiting");
		    wait();//等待读者发出notify
		   }
		   catch(Exception e){
		   }
		  
		  }
		  dbWriting =true;
		 }
		 
		 public synchronized void endWriting(){//结束写
		  --writerCount;
		  System.out.println("endWriting"+queue.size());
		    if(writerCount==0&&queue.size()!=0){//没有写者
		    dbWriting=false;
		  
		    for(Object o:queue)
			  {
		    
				  if(o.toString().equals("Reader"))
				  {
					  queue.remove();
					  notifyAll();
				  }else
				  {
					  notifyAll();
					  break;
				  }
			  }
		  }
		  //System.out.println("one writer is done writing. writerCount="+writerCount);
		  
		  //notifyAll();
		 }
		 
}

[baar]

读者类

public class Reader extends Thread{
	private Puffer C;
	 private int readerNum;
	 
	 public Reader(int r,Puffer db) {
	  readerNum=r;
	  C=db;
	 }
	 
	 public void run(){
	  int c;
	  while(true){
		  System.out.println("reader "+readerNum+" wants to read");
		   c=C.startRead(this);
		   System.out.println("reader "+readerNum+" is reading. readerCount="+c);
//		   try {
//				Thread.sleep(5);
//			} catch (InterruptedException e) {
//				// TODO Auto-generated catch block
//				e.printStackTrace();
//			}
		   c=C.endReading();
		   System.out.println("It is reader "+readerNum+" who has done reading. readercount="+c);
		  
	  }
//	  for ( int i = 0 ; i < 5 ; i++)
//	  {
//	   System.out.println("reader "+readerNum+" wants to read");
//	   c=C.startRead(this);  
//	   System.out.println("reader "+readerNum+" is reading. readerCount="+c);
//	   c=C.endReading();
//	   System.out.println("It is reader "+readerNum+" who has done reading. readercount="+c);
//	  
//	  }
	 }

	@Override
	public String toString() {
		// TODO Auto-generated method stub
		return "Reader";
	}
	 

写者类

public class Writer extends Thread{
	private Puffer C;
    private int writerNum;
 public Writer(int w,Puffer db) {
  writerNum=w;
  C=db;
 
 }
 
 public void run(){
  while(true)
	 {
		  System.out.println("Writer "+writerNum+" wants to write");
		   C.startWriting(this);
		 
		   System.out.println("Writer "+writerNum+" is writing");
//		   try {
//				Thread.sleep(50);
//			} catch (InterruptedException e) {
//				// TODO Auto-generated catch block
//				e.printStackTrace();
//			}
		   C.endWriting();
		   System.out.println("It is Writer "+writerNum+" who has done writing .");
	 }
//	  for ( int i = 0 ; i < 5 ; i++)
//	{
//   
//   System.out.println("Writer "+writerNum+" wants to write");
//   C.startWriting(this);
//   System.out.println("Writer "+writerNum+" is writing");
//   C.endWriting();
//   System.out.println("It is Writer "+writerNum+" who has done writing .");
//  
//  }
 
 }
}

[baar]

main方法

public class Test {
	public static void main(String args[])
	{
		Puffer p=new Puffer();
		
		  Reader r1=new Reader(1,p);//定义读者r1
		  Reader r2=new Reader(2,p);//定义读者r2
		  Reader r3=new Reader(3,p);
		  Writer w1=new Writer(1,p);//定义写者w1
		  Writer w2=new Writer(2,p);
		 
		  r1.start();
		  w1.start();
		  r2.start();
		  w2.start();
		  r3.start();
		   
	}
}