Improved UDPServer.java

As per our in-class discussion on 2002-02-22, Kurose and Ross's UDPClient.java program can be improved in the following ways:

There is no reason to allocate an array of 1024 bytes to initialize sendData, because this array becomes garbage without ever being used.
When the received data is converted into a String, not all 1024 bytes should be converted. Instead, the received packet's length should govern this.

import java.io.*;
import java.net.*;
class UDPServer {
    public static void main(String args[]) throws Exception
    {
        DatagramSocket serverSocket = new
            DatagramSocket(9876);
        byte[] receiveData = new byte[1024];
        byte[] sendData;
        while(true)
            {
                DatagramPacket receivePacket =
                    new DatagramPacket(receiveData, 
                                       receiveData.length);
                serverSocket.receive(receivePacket);
                String sentence = new String(
                                             receivePacket.getData(), 0, receivePacket.getLength());
                InetAddress IPAddress =
                    receivePacket.getAddress();
                int port = receivePacket.getPort();
                String capitalizedSentence = 
                    sentence.toUpperCase();
                sendData = capitalizedSentence.
                    getBytes();
                DatagramPacket sendPacket =
                    new DatagramPacket(sendData,
                                       sendData.length, 
                                       IPAddress, port);
                serverSocket.send(sendPacket);
            }
    }
}