Question

IN JAVA!

The field of cryptography is a very rich and fascinating branch that combines math and computer science. I encourage you to explore it more. For the time being though, in this lab assignment, we will focus on identifying most occurring letters in two different languages.

[You can then take your work a few steps further by applying it to deciphering by frequency analysis and see what happens!] To practice your skills in frequency analysis, you will be given two full books (txt version) to read (well, to have the computer parse J): one in French and one in English. They are the same book in two different languages: The Miserables, by Victor Hugo (some of you may have read it, or seen the recent movie about it). Your job will be to: • Parse each book; • As you parse the book, collect information about the number of times each letter of the alphabet occurs in the book (by using an array of 26 integers); and then • “Sort” this array (and maybe not just this array) to identify the 5 most frequent letters in English and the 5 most frequent letters in French.

Your goal is to write a few methods as follows: • FrequencyInBook: o Takes a txt file as input (TheMiserables-French.txt and then TheMiserablesEnglish.txt) as well as an alphabet o Returns an array of integers that contains the amount of times each letter occurred in the book (in our alphabet, it will be 26 integers, one per letter) • FiveMostFrequentLetters: o Takes as input the array that indicate the frequencies of all letters in the text o Takes an alphabet in the format of your choice o Returns the 5 most occurring letters • Main method: Below, you will find the pseudocode of your main method. You will have to write it in java in such a way that it uses your above 2 methods.

Use FrequencyInBook: Read TheMiserables-French.txt à array of frequencies FF Use FiveMostFrequentLetters: Identify and print out the 5 most frequent letters in the language under study as follows: “The French language has the following 5 most frequent letters: … ”

Followed by: Use FrequencyInBook: Read TheMiserables-English.txt à array of frequencies FE Use FiveMostFrequentLetters: Identify and print out the 5 most frequent letters in the language under study as follows: “The English language has the following 5 most frequent letters: …

Answer 1

// Java program to calculate the frequency of letters in a book and determine the top 5 frequent letters
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class BookFrequency {
  
   // method that counts the frequency of each letter in array alphabets in the input file filename
   public static int[] FrequencyInBook(String filename, String[] alphabets) throws FileNotFoundException
   {  
       int frequency[] = new int[alphabets.length]; // create an integer array of same length as the alphabets
       String line;
       // initialize the data for each frequency as 0
       for(int i=0;i<frequency.length;i++)
           frequency[i] = 0;
      
       File file = new File(filename); // open the file
       if(file.exists()) // if file exists
       {
           Scanner fileScan = new Scanner(file); // create a scanner object to read the file
          
           // loop to read till the end of file
           while(fileScan.hasNext())
           {
               line = fileScan.next(); // read a string from file
               // loop over the string and increment the frequency of the letters in the string
               for(int i=0;i<line.length();i++)
               {
                   // loop to find the index of the letter considered
                   for(int j=0;j<alphabets.length;j++)
                   {
                       if(line.substring(i,i+1).equalsIgnoreCase(alphabets[j]))
                       {
                           frequency[j]++;
                           break;
                       }
                      
                   }
               }
           }
          
           fileScan.close(); // close the file
       }
      
       return frequency; // return the frequency array
   }
  
   // method to find the top 5 most frequent letters in the letters array by the frequency given in frequency array
   public static String[] FiveMostFrequentLetters(int[] frequency, String[] letters)
   {
       int max;
       // sort the arrays by frequency in descending order
       for(int i=0;i<letters.length-1;i++)
       {
           max = i;
           for(int j=i+1;j<letters.length;j++)
           {
               if(frequency[j] > frequency[max])
                   max = j;
           }
          
           if(max != i)
           {
               int tempFreq = frequency[i];
               frequency[i] = frequency[max];
               frequency[max] = tempFreq;
              
               String tempLetter = letters[i];
               letters[i] = letters[max];
               letters[max] = tempLetter;
              
           }
       }
      
       // create an array of string to store the top 5 letters by frequency
       String top5[] = new String[5];
      
       for(int i=0;i<letters.length;i++)
           top5[i] = letters[i];
      
       return top5; // return the top5 array
   }

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

       // create an array of english alphabets
       String alphabets[] = {"A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z"};
       // get the frequency of letters in french book
       int frenchFreq[] = FrequencyInBook("TheMiserables-French.txt",alphabets);
       // get the frequency of letters in english book
       int englishFreq[] = FrequencyInBook("TheMiserablesEnglish.txt",alphabets);
      
       // get the top 5 most frequenct letters in english and french book
       String top5English[] = FiveMostFrequentLetters(englishFreq,alphabets);
       String top5French[] = FiveMostFrequentLetters(frenchFreq,alphabets);
      
       // display the top 5 frequent letters
       System.out.print("The French language has the following 5 most frequent letters: ");
       for(int i=0;i<top5French.length;i++)
           System.out.print(top5French[i]+" ");
      
       System.out.print("The English language has the following 5 most frequent letters: ");
       for(int i=0;i<top5English.length;i++)
           System.out.print(top5English[i]+" ");
   }

}
//end of program