一个java 的tcp聊天程序的客户端

import java.io.*;
import java.net.*;
import java.util.Scanner;


public  class client
{
	public static void main(String[] args)
	{
		work.link();
		new MyworkWriter().start();		
	}
}

class work
{
	//是否在线
	static boolean online=false;
	static Socket s1 =null;
	static BufferedReader in=null;	 
	static PrintWriter  out=null;	
	
	static void set_online()
	{
		online=true;
	}
	static void set_offline()
	{
		online=false;
	}
	static void link()
	{
		
		try{
		      //链接sever端
		      s1 = new Socket("127.0.0.1",9998);		     	
		      //实例化输入流     
		      in= new BufferedReader(new InputStreamReader(s1.getInputStream()));	
		      out=new PrintWriter(s1.getOutputStream(),true);
		      set_online();
		      System.out.println("已连接");
		      new  MyworkReader ().start();
		    }catch(SocketException e){
		    	 System.out.println("无法与对方主机建立连接");
		    	 set_offline();
		      System.out.println(e);
		    }catch(IOException e){
		    	System.out.println("输入输出出错");
		    	set_offline();
		      System.out.println(e);
		    }  
		
	}
	
}
//创建一个进程用来写入并发送数据
	 class MyworkWriter extends Thread
	{
		
	  
		public void run()
		{
		  InputStreamReader isr = new InputStreamReader(System.in);
		  BufferedReader br = new BufferedReader(isr);
		  String msg;
			try
			{
				while(true)
				{
					msg = br.readLine();
					msg = msg.trim();
					switch(msg)
					{
			    		case "exit":
			    		System.out.println("exit,程序退出");
			    		System.exit(0);
			    		break;
			    		case "link":
				    	System.out.println("link,连接远程主机");
				    	if(work.online)
						{
							
							System.out.println("在线状态,不能重复连接");
						}
						else
						{
							work.link();
						}
				    	break;
			    		case "help":
				    	System.out.println("help,帮助");
				    	System.out.println("exit,退出程序");
				    	System.out.println("link,连接主机");		
				    	System.out.println("close,关闭连接");
				    	break;	
			    		case "close":
					    	System.out.println("close,关闭连接");
					    	
					    	work.s1.close();
					    	break;	
				    	default:
				    		if(work.online)
							{
								work.out.println(msg);
							}
							else
							{
								System.out.println("你已经离线状态,为您重新连接服务器.");
								work.link();
								if(work.online)
								{
									work.out.println(msg);									
								}
								else
								{
									System.out.println("还是不能连接,可能远程服务器已经关闭.");
								}
								
							}
				    		
			    		
					}
					
					
				}
			}
			
	  		catch(IOException e)
	  		{
		    	System.out.println("发送数据时出错");
		    	System.out.println(e);
	  		}
	  }
	}
	//创建一个进程用来进行接收读取数据
	class MyworkReader extends Thread
	{
		public void run()
		{
			String msg;
			try
			{
				while(true)
				{
					msg = work.in.readLine();
					System.out.println("对方说:"+msg);
					if(msg.equals("bye"))
					{
						System.out.println("对方下线,程序退出");
						work.set_offline();
						break;
					}
				}
			}catch(IOException e)
			{
				System.out.println("读数据时出错,可能对方主机掉线");    	
				System.out.println(e);
				work.set_offline();
			}
		}
	}