ClientList.java

import java.util.*;
import java.io.*;

public class ClientList implements Serializable {
  private static final long serialVersionUID = 1L;
  private List<Client> clients = new LinkedList<Client>(); // Linked list of clients
  private static ClientList clientList;

  private ClientList() {
  }

  public static ClientList instance() { // check if an instance exists (singleton)
    if (clientList == null) {
      return (clientList = new ClientList());
    } else {
      return clientList;
    }
  }

  public boolean insertClient(Client client) {
    clients.add(client);
    return true;
  }

  public Iterator<Client> getClients() {
    return clients.iterator();
  }

  private void writeObject(java.io.ObjectOutputStream output) {
    try {
      output.defaultWriteObject();
      output.writeObject(clientList);
    } catch (IOException ioe) {
      ioe.printStackTrace();
    }
  }

  public Client search(String clientId) {
    for (Iterator<Client> iterator = clients.iterator(); iterator.hasNext();) {
      Client Client = (Client) iterator.next();
      if (Client.getId().equals(clientId)) {
        return Client;
      }
    }
    return null;
  }

  private void readObject(java.io.ObjectInputStream input) {
    try {
      if (clientList != null) {
        return;
      } else {
        input.defaultReadObject();
        if (clientList == null) {
          clientList = (ClientList) input.readObject();
        } else {
          input.readObject();
        }
      }
    } catch (IOException ioe) {
      ioe.printStackTrace();
    } catch (ClassNotFoundException cnfe) {
      cnfe.printStackTrace();
    }
  }

  public String toString() {
    return clients.toString();
  }
}