LAB EXERCISE 1: READ FROM URL

URLReader.java import java.net.*; import java.io.*;

public class URLReader { public static void main(String[] args) throws Exception { URL yahoo = new URL("http://www.lelong.com/"); BufferedReader in = new BufferedReader( new InputStreamReader( yahoo.openStream()));

String inputLine;

for ( int i =0;(inputLine = in.readLine()) != null; i++){ System.out.println(inputLine);}

in.close(); }
}

LAB EXERCISE 2: Echo Client

EchoClient .java import java.io.*; import java.net.*;

public class EchoClient
{
public static void main(String[] args) { try { Socket s = new Socket("127.0.0.1", 9999); BufferedReader r = new BufferedReader(new InputStreamReader(s.getInputStream())); PrintWriter w = new PrintWriter(s.getOutputStream(), true); BufferedReader con = new BufferedReader(new InputStreamReader(System.in)); String line; do { line = r.readLine(); if ( line != null ) System.out.println(line); line = con.readLine(); w.println(line); } while ( !line.trim().equals("bye") ); } catch (Exception err) { System.err.println(err); } }
}

LAB EXERCISE 3:MULTI THREADS

SimpleThreads.java public class SimpleThreads {

//Display a message, preceded by the name of the current thread static void threadMessage(String message) { String threadName = Thread.currentThread().getName(); System.out.format("%s: %s%n", threadName, message); }

private static class MessageLoop implements Runnable { public void run() { String importantInfo[] = { "GOOD MORNING", "NOW IT IS GOOD AFTERNOON", "GOOD EVENING", "GOOD NIGHT" }; try { for (int i = 0; i < importantInfo.length; i++) { //Pause for 4 seconds Thread.sleep(4000); //Print a message threadMessage(importantInfo[i]); } } catch (InterruptedException e) { threadMessage("I wasn't done!"); } } }

public static void main(String args[]) throws InterruptedException {

//Delay, in milliseconds before we interrupt MessageLoop //thread (default one hour). long patience = 1000 * 60 * 60;

//If command line argument present, gives patience in seconds. if (args.length > 0) { try { patience = Long.parseLong(args[0]) * 1000; } catch (NumberFormatException e) { System.err.println("Argument must be an integer."); System.exit(1); }

}

threadMessage("Starting MessageLoop thread"); long startTime = System.currentTimeMillis(); Thread t = new Thread(new MessageLoop()); t.start();

threadMessage("Waiting for MessageLoop thread to finish"); //loop until MessageLoop thread exits while (t.isAlive()) { threadMessage("Still waiting..."); //Wait maximum of 1 second for MessageLoop thread to //finish. t.join(1000); if (((System.currentTimeMillis() - startTime) > patience) && t.isAlive()) { threadMessage("Tired of waiting!"); t.interrupt(); //Shouldn't be long now -- wait indefinitely t.join(); }

} threadMessage("Finally!"); }
}

TCPServer.java import java.io.*; import java.net.*;

class TCPServer
{
public static void main(String argv[]) throws Exception { String clientSentence; String capitalizedSentence; ServerSocket welcomeSocket = new ServerSocket(20000);

while(true) { Socket connectionSocket = welcomeSocket.accept(); BufferedReader inFromClient = new BufferedReader(new InputStreamReader(connectionSocket.getInputStream())); DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream()); clientSentence = inFromClient.readLine(); System.out.println("Received: " + clientSentence); capitalizedSentence = clientSentence.toUpperCase() + '\n'; outToClient.writeBytes(capitalizedSentence); } }
}
UDPClient.java import java.net.*; import java.io.*;

class UDPClient
{
public static void main(String args[]) throws Exception { DatagramSocket dsoc=new DatagramSocket(40000); byte buff[]=new byte[1024]; DatagramPacket dpack=new DatagramPacket(buff,buff.length); dsoc.receive(dpack); System.out.println(new String(dpack.getData())); }
}

Deadlock.java public class Deadlock { static class Friend { private final String name; public Friend(String name) { this.name = name; } public String getName() { return this.name; } public synchronized void bow(Friend bower) { System.out.format("%s: %s IS MY NEW FRIEND!%n", this.name, bower.getName()); bower.bowBack(this); } public synchronized void bowBack(Friend bower) { System.out.format("%s: %s IS MY NEW FRIEND!%n", this.name, bower.getName()); } } public static void main(String[] args) { final Friend ROCK = new Friend("ROCK"); final Friend JOHN = new Friend("CENA"); new Thread(new Runnable() { public void run() { ROCK.bow(JOHN); } }).start(); new Thread(new Runnable() { public void run() { JOHN.bow(ROCK); } }).start(); } }

EchoServer .java import java.io.*; import java.net.*;

public class EchoServer
{
public EchoServer(int portnum) { try { server = new ServerSocket(portnum); } catch (Exception err) { System.out.println(err); } }

public void serve() { try { while (true) { Socket client = server.accept(); BufferedReader r = new BufferedReader(new InputStreamReader(client.getInputStream())); PrintWriter w = new PrintWriter(client.getOutputStream(), true); w.println("Welcome to the Java EchoServer. Type 'bye' to close."); String line; do { line = r.readLine(); if ( line != null ) w.println("Got: "+ line); } while ( !line.trim().equals("bye") ); client.close(); } } catch (Exception err) { System.err.println(err); } }

public static void main(String[] args) { EchoServer s = new EchoServer(9999); s.serve(); }

private ServerSocket server;
}

LAB EXERCISE 6: RMI

ReceiveMessageInterface.java import java.rmi.*;

public interface ReceiveMessageInterface extends Remote{ void receiveMessage(String x) throws RemoteException;
}

RmiClient.server.java import java.rmi.*; import java.rmi.registry.*; import java.net.*;

public class RmiClient{ static public void main(String args[]){ ReceiveMessageInterface rmiServer; Registry registry; String serverAddress=args[0]; String serverPort=args[1]; String text=args[2]; System.out.println ("sending " + text + " to " +serverAddress + ":" + serverPort); try{ registry=LocateRegistry.getRegistry (serverAddress,(new Integer(serverPort)).intValue()); rmiServer=(ReceiveMessageInterface)(registry.lookup("rmiServer")); // call the remote method rmiServer.receiveMessage(text); } catch(RemoteException e){ e.printStackTrace(); } catch(NotBoundException e){ System.err.println(e); } }
}

RmiServer.java import java.rmi.*; import java.rmi.registry.*; import java.rmi.server.*; import java.net.*;

public class RmiServer extends java.rmi.server.UnicastRemoteObject implements ReceiveMessageInterface{ String address; Registry registry;

public void receiveMessage(String x) throws RemoteException{ System.out.println(x); } public RmiServer() throws RemoteException{ try{ address = (InetAddress.getLocalHost()).toString(); } catch(Exception e){ System.out.println("can't get inet address."); } int port=3232; System.out.println("this address=" + address + ",port=" + port); try{ registry = LocateRegistry.createRegistry(port); registry.rebind("rmiServer", this); } catch(RemoteException e){ System.out.println("remote exception"+ e); } } static public void main(String args[]){ try{ RmiServer server = new RmiServer(); } catch (Exception e){ e.printStackTrace(); System.exit(1); } }
}

UDPServer.java import java.net.*; import java.io.*; import java.util.*;

class UDPServer
{
public static void main(String args[]) throws Exception { DatagramSocket dsoc=new DatagramSocket(40000); InetAddress host=InetAddress.getLocalHost(); String str=(new Date()).toString(); byte buf[]=str.getBytes(); dsoc.send(new DatagramPacket(buf,buf.length,host,24)); dsoc.close(); }
}

LAB EXERCISE 6: RMI

WebBrowser.java import java.awt.*; import java.awt.event.*; import java.util.*; import java.net.*; import java.io.*; import javax.swing.*; import javax.swing.event.*;

public class WebBrowser
{
public static void main(String [] args) { JFrame frame = new EditorPaneFrame(); frame.show(); }
}
class EditorPaneFrame extends JFrame
{

private JTextField url; private JCheckBox editable; private JButton loadButton; private JButton backButton; private JEditorPane editorPane; private Stack urlStack = new Stack();

public EditorPaneFrame() { setTitle("Java Web Browser"); setSize(600,400); addWindowListener(new WindowAdapter() { public void windowClosing(WindowEvent e) { System.exit(0); } } );

// set up text field and load button for typing in URL

url = new JTextField(50);

loadButton = new JButton("Load"); loadButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent event) { try { // remember URL for back button urlStack.push(url.getText()); editorPane.setPage(url.getText()); } catch(Exception e) { editorPane.setText("Error: " +e); } } });

// set up back button and button action

backButton = new JButton("Back"); backButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent event) { if(urlStack.size()<=1) return; try { urlStack.pop(); String urlString = (String)urlStack.peek(); url.setText(urlString); editorPane.setPage(urlString); } catch(IOException e) { editorPane.setText("Error : " +e); } } });

editorPane = new JEditorPane(); editorPane.setEditable(false); editorPane.addHyperlinkListener(new HyperlinkListener() { public void hyperlinkUpdate(HyperlinkEvent event) { if(event.getEventType() == HyperlinkEvent.EventType.ACTIVATED) { try { urlStack.push(event.getURL().toString()); url.setText(event.getURL().toString());

editorPane.setPage(event.getURL()); } catch(IOException e) { editorPane.setText("Error: " + e); } } } });

editable = new JCheckBox(); editable.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent event) { editorPane.setEditable(editable.isSelected()); } });

Container contentPane = getContentPane(); contentPane.add(new JScrollPane(editorPane), "Center");

JPanel panel = new JPanel(); panel.add(new JLabel("URL")); panel.add(url); panel.add(loadButton); panel.add(backButton); panel.add(new JLabel("Editable")); panel.add(editable);

contentPane.add(panel,"South"); }

}