I am using a PriorityBlockingQueue in my server program for a network printer manager, but the thing is whenever I print the size of the queue its always 1. I think it is cause i am using threads in my program to support multiple clients. How do i solve this problem? And can I print the queue with out removing the objects in the queue?
The queue contains objects of PrintJob class.
The code for the server is below....

import java.net.*;
import java.io.*;
import javax.swing.*;
import java.util.concurrent.PriorityBlockingQueue;
import java.util.Comparator;


public class Server_Frame extends javax.swing.JFrame {
     
    /** Creates new form Server_Frame */
    public Server_Frame() {
        initComponents();
        
    }

    /** This method is called from within the constructor to
     * initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is
     * always regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setTitle("Network Printer Manager - Server");

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 616, Short.MAX_VALUE)
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 370, Short.MAX_VALUE)
        );

        pack();
    }// </editor-fold>                        

    /**
    * @param args the command line arguments
    */
    public static void main(String args[])throws IOException
    {
        java.awt.EventQueue.invokeLater(new Runnable()
        {
            public void run() {
                new Server_Frame().setVisible(true);
            }
        });
        Server server = new Server();
        server.connect();
        
    }                  
}


class Server implements Runnable
{
        ServerSocket sock;
	Socket client = null;
	ObjectOutputStream out;
	ObjectInputStream in;
        public JobQ jq = new JobQ(); //creating an object of the q
        int count=0;
        int ID;

        Server()
        { }

        Server(Socket s,int i)
        {
            this.client = s;
            this.ID = i;
        }

        void connect()
        {
            try
            {
               sock = new ServerSocket(5000);

               while(true)
               {
                 client = sock.accept();
                 JOptionPane.showMessageDialog(null,"Client Connected","Connected",JOptionPane.INFORMATION_MESSAGE);
                 //PrintJob pj = new PrintJob();
                  Runnable runnable = new Server(client, ++count);
                  Thread thread = new Thread(runnable);
                  thread.start();
                 
               }
            }

            catch(Exception e)
            {
                JOptionPane.showMessageDialog(null,e,"Error",JOptionPane.ERROR_MESSAGE);
            }
        }
        
        public void run()
        {
            try
            {
                out = new                    ObjectOutputStream(client.getOutputStream());
	        out.flush();

                in = new ObjectInputStream(client.getInputStream());
            }
            catch(Exception e)
            {
                JOptionPane.showMessageDialog(null,e,"Error",JOptionPane.ERROR_MESSAGE);
            }

               String u = (String)recieve_from_client();
               System.out.println(u);
               String p = (String)recieve_from_client();
               System.out.println(p);

               String flag = authenticate(u, p);
               System.out.print(flag);
               send_to_client(flag);

               if(flag.equals("false"))
               {
                   try
                   {
                       client.close();
                   }
                   catch(Exception e)
                   {
                       JOptionPane.showMessageDialog(null,e,"Error",JOptionPane.ERROR_MESSAGE);
                   }
               }
               get_Job();

               jq.PrintQ(); //printing the q
               
        }

        void send_to_client(Object s)
        {
            try
            {
                out.writeObject(s);
		out.flush();
            }

            catch(Exception e)
            {
                JOptionPane.showMessageDialog(null,e,"Error",JOptionPane.ERROR_MESSAGE);
            }
        }

        Object recieve_from_client()
        {
            Object s = null;

            try
            {
                s = in.readObject();

            }
            catch(Exception e)
            {
                JOptionPane.showMessageDialog(null,e,"Error",JOptionPane.ERROR_MESSAGE);
            }

            return s;
        }

        String authenticate(String usr ,String pwd)
        {
            String n=null,p=null;
            
            try
            {
              FileReader fn=new FileReader("username.txt");
              BufferedReader fnbr=new BufferedReader(fn);

              FileReader fp=new FileReader("password.txt");
              BufferedReader fpbr=new BufferedReader(fp);

              while(((n=fnbr.readLine())!=null)&&(p=fpbr.readLine())!=null)
              {  
                  if(n.equals(usr))
                  {
                      if(p.equals(pwd))
                         return "true";
                  }
              }
              
            }
            catch(Exception e)
            {
               JOptionPane.showMessageDialog(null,e,"Error",JOptionPane.ERROR_MESSAGE);
            }
            return "false";
        }

       void get_Job()
       {
          PrintJob pj = new PrintJob();
          pj.file_name = (String)this.recieve_from_client();
          System.out.println(pj.file_name);
          String temp=" ";
          try
          {
             FileWriter fw = new FileWriter(pj.file_name);
             BufferedWriter fbw = new BufferedWriter(fw);

             while(!(temp=(String)this.recieve_from_client()).equals("stop"))
             {
                 //temp = this.recieve_from_client();
                 fbw.write(temp);
                 fbw.newLine();
                 fbw.flush();
                 System.out.println(temp);
             }
             fbw.close();
             fw.close();

             pj.priority = (Integer)this.recieve_from_client();
             System.out.println(pj.priority);
             pj.no_of_copies = (Integer)this.recieve_from_client();
             System.out.println(pj.no_of_copies);

             jq.insertJob(pj);
          }
          catch(Exception e)
         {
            JOptionPane.showMessageDialog(null,e,"SError",JOptionPane.ERROR_MESSAGE);
         }
       }

}

 class PrintJob
 {
     String file_name;
     int priority;
     Object no_of_copies;

     PrintJob()
     { }
 }

 class JobQ
 {
      PriorityBlockingQueue<PrintJob> pq =null;
      Comparator <Object> comparator = new PriorityComparer();

      JobQ()
      {
          pq = new PriorityBlockingQueue(20,comparator);
      }

      void insertJob(PrintJob job)
      {
          pq.add(job);
      }

      void PrintQ()
      {
          PrintJob j=null;
          PriorityBlockingQueue<PrintJob> q = new PriorityBlockingQueue();
          int i;
        
          System.out.println(pq.size()); //printing the size
          
         /* while(!pq.isEmpty())    //Trying to print q...will this work?
          {
              for(i=0;i<pq.size();i++)
              {
                 j=pq.poll();
                 System.out.println(j.priority);
                 q.add(j);
              }
                  
          }

          while(!q.isEmpty())
          {
              for(i=0;i<q.size();i++)
              {
                 j=q.poll();
                 //System.out.println(j.priority);
                 pq.add(j);
              }

          }*/
      }
 }

 class PriorityComparer implements Comparator<Object>
 {
     public int compare(Object j1, Object j2)
     {
          int p1 = ((PrintJob)j1).priority;
          int p2 = ((PrintJob)j2).priority;

          if(p1>p2)
              return 1;

          else if(p1<p2)
              return -1;

          else
              return 0;
     }
 }

Good luck in finding help as you won't get it here people are too of themselves to help us :(. Try a more helpful forum like dream.in.code :)

try synchronizing things. It is indeed possible you're printing the content of the queue in one thread while another is waiting to insert into it.

try synchronizing things. It is indeed possible you're printing the content of the queue in one thread while another is waiting to insert into it.

How do i go about doing that? Any examples or something....???

This article has been dead for over six months. Start a new discussion instead.