Question

Question II

This question carries 50% of the marks for this assignment.

This question is about avoiding race condition by using synchronization mechanism provided by the JAVA programming language. We provided you with a Netbeans JAVA project. The project idea is as follows: we want to merge the content of four files into a single file, as follows. Below is the content of all four files:

F1 content: 1 1 1 1

F2 content: 2 2 2 2

F3 content: 3 3 3 3

F4 content: 4 4 4 4

After merging them into the Sink file, we expect the following content in the sink file:1234123412341234

We want to read from each file only one integer value at a time (starting form file number 1, number 2 and so on) and write theses integers values ( in the same order we read them) into a specific sink file, we want to repeat it until all file files are empty.

Please note that all files have the same number of integers.

We have provided you with a template project that needs to be modified to accomplish the above task correctly.

The project is composed of the following classes including four text files:

Four text files called “f1.txt”, “f2.txt”, “f3.txt” and “f4.txt”, each file has a sequence of integer corresponding its name, for instance “f2.txt” contains a sequence of integers all are 2.

The following JAVA source code files are included in the NetBeans projects:

WriteToFile: A helper class to write into a file.

SyncWriteToFile: which control the access to the file, it does so by aggregating an object of the class “WriteToFile”

MergeFiles that extends Thread: it is intended to read all integers form a specific file and use an object of “SyncWriteToFile” to write them into the sink file at the appropriate place.

TMA_Tm298_SummerEgJo: contains the main method to test the program

Read the source code of the above classes carefully and run the project. You will discover that the content of the sink file is not as expected and each time you run it you got a different content. Provide screen shots form running the project without any modification. Provide convincing justification, why you got these results. [15 marks]

In order to get the expected sink file content, you need to modify the project as follows:

You can do so by first identifying the shared resources and then the critical section code in the project. [10 marks]. Then you need to change the critical section code so that the sink file contains the following result no matter how many times you run the project. The sink file correct content is :1234123412341234. [25 marks]

You are sked to submit the whole project (as one zip file) after all modification.

Answer 1

// PLEASE LIKE THE SOLUTION
// FEEL FREE TO DISCUSSION IN COMMENT SECTION
// JAVA PROGRAM

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

class WriteToFiles{
   // attribute to store file writer
   public static void writeFile(FileWriter myWriter,char a){
       try{
           myWriter.write(a);
       }
       catch(Exception e){
           System.out.println(e.getMessage());
       }
   }
}

class MergeFiles extends Thread{
   // run method
   // attribute
   // writer file
   static FileWriter myWriter;
  
   // reader file
   static FileReader reader;

   public void run(){
       try{
           // read and write to file
           int i;
           if((i = reader.read()) != -1){
               WriteToFiles wr = new WriteToFiles();
               wr.writeFile(myWriter,(char)i);
               Test.done = 0;
           }
           else{
               Test.done++;
           }
       }
       catch (Exception e){
           // message
           System.out.println ("Exception is caught");
       }
   }
}

// Test
class Test{
   // attribute
   static int done = 0;

   public static void main(String rg[]){

       try{

           MergeFiles.myWriter = new FileWriter(new File("output.txt"));
           FileReader file1 = new FileReader(new File("f1.txt"));
           FileReader file2 = new FileReader(new File("f2.txt"));
           FileReader file3 = new FileReader(new File("f3.txt"));
           FileReader file4 = new FileReader(new File("f4.txt"));

           // now call reader writer in sync way
           while(Test.done != 4){

               MergeFiles.reader = file1;
               MergeFiles r1 = new MergeFiles();
               r1.run();
               r1.join();

               MergeFiles.reader = file2;
               MergeFiles r2 = new MergeFiles();
               r2.run();
               r2.join();

               MergeFiles.reader = file3;
               MergeFiles r3 = new MergeFiles();
               r3.run();
               r3.join();

               MergeFiles.reader = file4;
               MergeFiles r4 = new MergeFiles();
               r4.run();
               r4.join();
           }

           // now close files
           MergeFiles.myWriter.close();
       }
       catch(Exception e){
           System.out.println(e.getMessage());
       }
   }

}

// SAMPLE OUTPUT

f1.txt x 1111

F2.txt x 2222

f3.txt 3333

f4.txt 4444

output.txt x Syn 1234123412341234