NullPointException in EmailServer EmailClient program
Hi, i'm working on a simple email server and email client program. But i get a NullPointException while using it.
I tried several solution by changing the code a bit, but i can't get it right. I could really use some help, thanks in advance.
import java.io.*;
import java.net.*;
publicclass EmailServer
{
privatestatic ServerSocket servSock;
privatestaticfinalint PORT = 1234;
privatestaticfinal String client1 ="Dave";
privatestaticfinal String client2 ="Karen";
privatestaticfinalint MAX_MESSAGES = 10;
privatestatic String[] mailbox1 =
new String[MAX_MESSAGES];
privatestatic String[] mailbox2 =
new String[MAX_MESSAGES];
privatestaticint messagesInBox1 = 0;
privatestaticint messagesInBox2 = 0;
publicstaticvoid main(String[] args)
{
System.out.println("Opening connection...\n");
try
{
servSock =new ServerSocket(PORT);
}
catch(IOException e)
{
System.out.println("Unable to attach to port!");
System.exit(1);
}
do
{
try
{
run();
}
catch (InvalidClientException icException)
{
System.out.println("Error: " + icException);
}
catch (InvalidRequestException irException)
{
System.out.println("Error: " + irException);
}
}while (true);
}
privatestaticvoid run()
throws InvalidClientException, InvalidRequestException
{
try
{
Socket link = servSock.accept();
BufferedReader in =
new BufferedReader(
new InputStreamReader(
link.getInputStream()));
PrintWriter out =new PrintWriter(
link.getOutputStream(),true);
String name = in.readLine();
String sendRead = in.readLine();
if (!name.equals(client1) && !name.equals(client2))
thrownew InvalidClientException();
if (!sendRead.equals("send") &&
!sendRead.equals("read"))
thrownew InvalidRequestException();
System.out.println("\n" + name +" " + sendRead
+"ing mail...");
if (name.equals(client1))
if (sendRead.equals("send"))
{
doSend(mailbox2,messagesInBox2,in);
if (messagesInBox2<MAX_MESSAGES)
messagesInBox2++;
}
else
{
doRead(mailbox1,messagesInBox1,out);
messagesInBox1 = 0;
}
else//From client2.
if (sendRead.equals("send"))
{
doSend(mailbox1,messagesInBox1,in);
if (messagesInBox1><MAX_MESSAGES)
messagesInBox1++;
}
else
{
doRead(mailbox2,messagesInBox2,out);
messagesInBox2 = 0;
}
link.close();
}
catch(IOException e)
{
e.printStackTrace();
}
}
privatestaticvoid doSend(String[] mailbox,
int messagesInBox, BufferedReader in)throws IOException
{
String message = in.readLine();
if (messagesInBox == MAX_MESSAGES)
System.out.println("\nMessage box full!");
else
mailbox[messagesInBox] = message;
}
privatestaticvoid doRead(String[] mailbox,
int messagesInBox, PrintWriter out)throws IOException
{
System.out.println("\nSending " + messagesInBox
+" message(s).\n");
out.println(messagesInBox);
for (int i=0; i><messagesInBox; i++)
out.println(mailbox[i]);
}
}
class InvalidClientExceptionextends Exception
{
public InvalidClientException()
{
super("Invalid client name!");
}
public InvalidClientException(String message)
{
super(message);
}
}
class InvalidRequestExceptionextends Exception
{
public InvalidRequestException()
{
super("Invalid request!");
}
public InvalidRequestException(String message)
{
super(message);
}
}
import java.io.*;
import java.net.*;
publicclass EmailClient
{
privatestatic InetAddress host;
privatestaticfinalint PORT = 1234;
privatestaticfinal String client1 ="Dave";
privatestaticfinal String client2 ="Karen";
privatestatic String name;
privatestatic BufferedReader in, userEntry;
privatestatic PrintWriter out;
publicstaticvoid main(String[] args)throws IOException
{
try
{
host = InetAddress.getLocalHost();
}
catch(UnknownHostException e)
{
System.out.println("Host ID not found!");
System.exit(1);
}
userEntry =new BufferedReader(
new InputStreamReader(System.in));
do
{
System.out.print(
"\nEnter name ('Dave' or 'Karen'): ");
name = userEntry.readLine();
}while (!name.equals(client1) && !name.equals(client2));
run();
}
privatestaticvoid run()throws IOException
{
String option, message, response;
do
{
Socket link =new Socket(host, PORT);
BufferedReader in =
new BufferedReader(
new InputStreamReader(
link.getInputStream()));
PrintWriter out =new PrintWriter(
link.getOutputStream(),true);
do
{
System.out.print("\nEnter 's' to send a message"
+" or 'r' to read message(s): ");
option = userEntry.readLine();
}while (!option.equals("s") && !option.equals("r"));
if (option.equals("s"))
doSend();
else
doRead();
link.close();
System.out.print("\nDo you wish to send/read again? (y/n) : ");
option = userEntry.readLine();
}while (!option.equals("n"));
}
privatestaticvoid doSend()throws IOException
{
System.out.println("\nEnter 1-line message: ");
String message = userEntry.readLine();
out.println(name);
out.println("send");
out.println(message);
}
privatestaticvoid doRead()throws IOException
{
out.println (name);
out.println("read");
int count = in.read();
String dummy = in.readLine();
if (count == 0)
System.out.println("\nMailbox empty.\n");
else
System.out.println("\nMessages:\n");
String message;
for (int i=0; i><count; i++)
{
message = in.readLine();
System.out.println(message);
}
}
}
Screenshot of the error: http://i7.tinypic.com/53ry8te.jpg>
