java interfaces - Page 531

Why do I get a nullpointerexception at line ds.getPort in class L1?

- by Fred

import java.awt.; import java.awt.event.; import javax.swing.; import java.io.; import java.net.; import java.util.; public class Draw extends JFrame { /* * Socket stuff */ static String host; static int port; static int localport; DatagramSocket ds; Socket socket; Draw d; Paper p = new Paper(ds); public Draw(int localport, String host, int port) { d = this; this.localport = localport; this.host = host; this.port = port; try { ds = new DatagramSocket(localport); InetAddress ia = InetAddress.getByName(host); System.out.println("Attempting to connect DatagramSocket. Local port " + localport + " , foreign host " + host + ", foreign port " + port + "..."); ds.connect(ia, port); System.out.println("Success, ds.localport: " + ds.getLocalPort() + ", ds.port: " + ds.getPort() + ", address: " + ds.getInetAddress()); Reciever r = new Reciever(ds); r.start(); } catch (Exception e) { e.printStackTrace(); } setDefaultCloseOperation(EXIT_ON_CLOSE); getContentPane().add(p, BorderLayout.CENTER); setSize(640, 480); setVisible(true); } public static void main(String[] args) { int x = 0; for (String s : args){ if (x==0){ localport = Integer.parseInt(s); x++; } else if (x==1){ host = s; x++; } else if (x==2){ port = Integer.parseInt(s); } } Draw d = new Draw(localport, host, port); } } class Paper extends JPanel { DatagramSocket ds; private HashSet hs = new HashSet(); public Paper(DatagramSocket ds) { this.ds=ds; setBackground(Color.white); addMouseListener(new L1(ds)); addMouseMotionListener(new L2()); } public void paintComponent(Graphics g) { super.paintComponent(g); g.setColor(Color.black); Iterator i = hs.iterator(); while(i.hasNext()) { Point p = (Point)i.next(); g.fillOval(p.x, p.y, 2, 2); } } private void addPoint(Point p) { hs.add(p); repaint(); } class L1 extends MouseAdapter { DatagramSocket ds; public L1(DatagramSocket ds){ this.ds=ds; } public void mousePressed(MouseEvent me) { addPoint(me.getPoint()); Point p = me.getPoint(); String message = Integer.toString(p.x) + " " + Integer.toString(p.y); System.out.println(message); try{ byte[] data = message.getBytes("UTF-8"); //InetAddress ia = InetAddress.getByName(ds.host); String convertedMessage = new String(data, "UTF-8"); System.out.println("The converted string is " + convertedMessage); DatagramPacket dp = new DatagramPacket(data, data.length); System.out.println(ds.getPort()); //System.out.println(message); //System.out.println(ds.toString()); //ds.send(dp); /*System.out.println("2Sending a packet containing data: " +data +" to " + ia + ":" + d.port + "...");*/ } catch (Exception e){ e.printStackTrace(); } } } class L2 extends MouseMotionAdapter { public void mouseDragged(MouseEvent me) { addPoint(me.getPoint()); Point p = me.getPoint(); String message = Integer.toString(p.x) + " " + Integer.toString(p.y); //System.out.println(message); } } } class Reciever extends Thread{ DatagramSocket ds; byte[] buffer; Reciever(DatagramSocket ds){ this.ds = ds; buffer = new byte[65507]; } public void run(){ try { DatagramPacket packet = new DatagramPacket(buffer, buffer.length); while(true){ try { ds.receive(packet); String s = new String(packet.getData()); System.out.println(s); } catch (Exception e) { e.printStackTrace(); } } } catch (Exception e) { e.printStackTrace(); } } }

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