Task - Packages - Creating and Using Packages

[akash-coded]

Assume you have written some classes. Belatedly, you decide they should be split into three packages, as listed in the following table. Furthermore, assume the classes are currently in the default package (they have no package statements).

Package Name	Class Name
mygame.server	Server
mygame.shared	Utilities
mygame.client	Client

Questions

1. Which line of code will you need to add to each source file to put each class in the right package?
2. To adhere to the directory structure, you will need to create some subdirectories in the development directory and put source files in the correct subdirectories. What subdirectories must you create? Which subdirectory does each source file go in?
3. Do you think you'll need to make any other changes to the source files to make them compile correctly? If so, what?

Exercises

Download the source files as listed here.

• Client
• Server
• Utilities

1. Implement the changes you proposed in questions 1 through 3 using the source files you just downloaded.
2. Compile the revised source files. (Hint: If you're invoking the compiler from the command line (as opposed to using a builder), invoke the compiler from the directory that contains the mygame directory you just created.)

Solution

Check your answers.

[NavneetBais]

Server

package mygame.server;

import mygame.utilities.*;
import mygame.client.*;
import java.io.*;
import java.net.*;
public class Server {
	public static void main(String args[]) throws IOException {
		ServerSocket serverSocket = null;

		Utilities.printMsg("creating server socket");
		
		try {
		    serverSocket = new ServerSocket(4445);
		} catch (IOException e) {
		    System.err.println("Unable to create server socket, " + e);
		    System.exit(1);
		    
		}

		Utilities.printMsg("accepting client connections");

		while (true) {
		    try {
			Socket clientSocket = serverSocket.accept();
			new Client(clientSocket);
		    } catch (IOException e) {
			System.err.println("Unable to accept socket connection, " + e); 
			System.exit(1);
		    }
		}
		
	    }
}

Client

package mygame.client;
import mygame.utilities.*;
import mygame.server.*;
import java.io.*;
import java.net.*;
import java.util.*;

public class Client {

		Socket clientSocket = null;

	    public Client(Socket s) {
	        clientSocket = s;
	    }

	    public void run() {
	        if (clientSocket == null) {
	            return;
	        }

	        Utilities.printMsg("creating output stream");

	        try (Socket localSocket = clientSocket;
	            PrintStream out = new PrintStream(localSocket.getOutputStream())) {
	            
	            Utilities.printMsg("writing current date");
	            Date d = new Date();
	            out.println(d);
	        
	        } catch (IOException e) {
	            System.err.println("IOException occurred, " + e);
	        } finally {
	            clientSocket = null;
	        }
	    }
	    
}

Utilities

package mygame.utilities;

public class Utilities {
	// set DEBUG = false and compile to stop debug messages
    final static boolean DEBUG = true;

    public static void printMsg(String msg) {
	if (DEBUG) {
	    System.out.println(msg);
	}
    }
}

Directory and Output

[ShravanKV2310]

Client

Server

Utilities

package myname.client;

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

import myname.utilities.Utilities;

public class Client extends Thread {
    Socket clientSocket = null;

    public Client(Socket s) {
        clientSocket = s;
    }

    public void run() {
        if (clientSocket == null) {
            return;
        }

        Utilities.printMsg("creating output stream");

        try (Socket localSocket = clientSocket;
            PrintStream out = new PrintStream(localSocket.getOutputStream())) {
            
            Utilities.printMsg("writing current date");
            Date d = new Date();
            out.println(d);
        
        } catch (IOException e) {
            System.err.println("IOException occurred, " + e);
        } finally {
            clientSocket = null;
        }
    }
}
# Server

package myname.server;

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

import myname.client.Client;
import myname.utilities.Utilities;

public class Server {

    public static void main(String args[]) {
	ServerSocket serverSocket = null;

	Utilities.printMsg("creating server socket");
	
	try {
	    serverSocket = new ServerSocket(4444);
	} catch (IOException e) {
	    System.err.println("Unable to create server socket, " + e);
	    System.exit(1);
	}

	Utilities.printMsg("accepting client connections");

	while (true) {
	    try {
		Socket clientSocket = serverSocket.accept();
		new Client(clientSocket).start();
	    } catch (IOException e) {
		System.err.println("Unable to accept socket connection, " + e); 
		System.exit(1);
	    }
	}
    }
}

# Utilities
package myname.utilities;

public class Utilities {
    // set DEBUG = false and compile to stop debug messages
    final static boolean DEBUG = true;

    public static void printMsg(String msg) {
	if (DEBUG) {
	    System.out.println(msg);
	}
    }
}

[ShravanKV2310]

[rrajbanshi]

server

package mygame.server;
import mygame.client.*;
import mygame.utilities.*;

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

public class Server {

    public static void main(String args[]) {
	ServerSocket serverSocket = null;

	Utilities.printMsg("creating server socket");
	
	try {
	    serverSocket = new ServerSocket(4444);
	} catch (IOException e) {
	    System.err.println("Unable to create server socket, " + e);
	    System.exit(1);
	}

	Utilities.printMsg("accepting client connections");

	while (true) {
	    try {
		Socket clientSocket = serverSocket.accept();
		new Client(clientSocket).start();
	    } catch (IOException e) {
		System.err.println("Unable to accept socket connection, " + e); 
		System.exit(1);
	    }
	}
    }
}

client

package mygame.client;

import mygame.server.*;
import mygame.utilities.*;

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

public class Client extends Thread {
    Socket clientSocket = null;

    public Client(Socket s) {
        clientSocket = s;
    }

    public void run() {
        if (clientSocket == null) {
            return;
        }

        Utilities.printMsg("creating output stream");

        try (Socket localSocket = clientSocket;
            PrintStream out = new PrintStream(localSocket.getOutputStream())) {
            
            Utilities.printMsg("writing current date");
            Date d = new Date();
            out.println(d);
        
        } catch (IOException e) {
            System.err.println("IOException occurred, " + e);
        } finally {
            clientSocket = null;
        }
    }
}

utilities

package mygame.utilities;
import mygame.client.*;
import mygame.server.*;
public class Utilities {
    // set DEBUG = false and compile to stop debug messages
    final static boolean DEBUG = true;

    public static void printMsg(String msg) {
	if (DEBUG) {
	    System.out.println(msg);
	}
    }
}