Goal: Modify the classes Transaction (from Project4), TransactionChecker (Observ

Question

Goal: Modify the classes Transaction (from Project4), TransactionChecker (Observable), TransactionLogger (Observer),as specified in Details 2 and 3. Write a TransactionChecker class as specified in Detail 4

Create a project (named Proj4bSmith if Smith is your last name) that consists of these files:

TransactionChecker.java  TransactionLogger.java TestTransactionChecker.java

Transaction.java (from Project 4).

Also download the transactions.txt file. Place it in the project folder.
Modify the TransactionChecker class:

Make this class a derived class that extends the base class Observable.

In the while loop, replace the printf statement with code that creates a Transaction object. For the transaction id, use an autogenerated id that starts with 1001 and increases by 1 for each new Transaction object created.

After the Transaction object is created in the while loop, write an if statement that notifies the observers if a transaction is found where amount is greater than $50,000 and the buyer is Eugene Eko. Notify all observers by sending them the Transactionobject. To do this, use the Observable methods setChanged and notifyObservers.

Modify the TransactionLogger class:

Have it implement the Observable interface, which means that an update method is required.

Add an update method with this header:

Write the info object (which is actually a Transaction object) out to the log file. After that, flush the output buffer, which forces the info be written to disk. Don't forget the @Override statement, which indicates that you are either overriding a method from a base class or implementing a required method from an interface.
Write a TestTransactionChecker class. In a main method:

Declare and instantiate a new TransactionChecker object.

Declare and instantiate a new TransactionLogger object.

Add the TransactionLogger object as an observer to the TransactionChecker object.

Call the checkTransactions method of the TransactionChecker object.

Transaction class from project 4:

public class Transaction {

   private int _id;

   private String _buyer;

   private String _seller;

   private double _amount;

   private String _timestamp;

   public Transaction() {};

   public Transaction(int _id, String _buyer, String _seller, double _amount, String _timestamp) {

       this._id = _id;

       this._buyer = _buyer;

       this._seller = _seller;

       this._amount = _amount;

       this._timestamp = _timestamp;

   }

       public int getId() {

       return _id;

   }

   public String getBuyer() {

       return _buyer;

   }

   public String getSeller() {

       return _seller;

   }

   public double getPrice() {

       return _amount;

   }

   public String toString() {

       return "_id: " + _id + " _buyer:" + _buyer + " _seller: " + _seller;

   }

}

Explanation / Answer

package Proj4bShubham;

import java.io.File;

import java.io.FileNotFoundException;

import java.util.Observable;

import java.util.Scanner;

public class TransactionChecker extends Observable{

Scanner _in;

public TransactionChecker(String fileName)

throws FileNotFoundException {

_in = new Scanner(new File(fileName));

}

public void checkTransactions( ) {

   int i = 1001;

while(_in.hasNextLine( )) {

String line = _in.nextLine( );

String[ ] fields = line.split(",");

Transaction trans = new Transaction(i,fields[0],fields[1],Double.parseDouble(fields[2]),fields[3]);

i++;

if (trans.getBuyer().equalsIgnoreCase("Eugene Eko") && trans.getPrice() > 50000 ) {

   setChanged();

   notifyObservers(trans);

}

}

_in.close( );

}

}

package Proj4bShubham;

import java.io.FileNotFoundException;

import java.io.PrintWriter;

import java.util.Observable;

import java.util.Observer;

public class TransactionLogger implements Observer{

PrintWriter _log;

public TransactionLogger(String fileName)

throws FileNotFoundException {

_log = new PrintWriter(fileName);

}

@Override

public void update(Observable obs, Object info){

   _log.println(info.toString());

   _log.flush();

}

}

package Proj4bShubham;

public class TestTransactionChecker {

   public static void main(String[] args) {

       // TODO Auto-generated method stub

       try{

       TransactionChecker checker = new TransactionChecker("transactions.txt");

       TransactionLogger logger = new TransactionLogger("logger.txt");

       checker.addObserver(logger);

       checker.checkTransactions();

       }

       catch(Exception e){

           e.printStackTrace();

       }

   }

}

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