Question

Hi guys, I'm working on an assignment for my Java II class and the narrative for this week's program has me a bit lost. I've put the narrative of the assignment in the quotation marks below.

" Included with this assignment is an encrypted text file. A simple Caesar cipher was used to encrypt the data. You are to create a program which will look at the frequency analysis of the letters (upper and lowercase) to help “crack” the code

A simple Caesar cipher was used to encrypt the data. You are to create a program which will look at the frequency analysis of the letters (upper and lowercase) to help “crack” the code. To help a bit: Using their ASCII codes, a Caesar cipher was used to encrypt uppercase letters, uppercase letters, and digits. This means the shift for uppercase letters forces the encrypted data to still be in the A-Z range. Lowercase letters will still be in the a-z range, and digits will be in the 0-9 range.

Your job is it so create a frequency analysis of the alphabetic characters in the file. To do this: Read a record from the file, look at each character in the record, count the frequency for each letter A-Z and a-z. You can use an array to keep the counts. Display the frequency distribution (percentage for each letter) in a GUI. "

So to put this frankly, I'm a bit lost. I know how to read the file, but I'm having a mini-stroke figuring out how to count all of the characters and their frequency. This is what I've got to read the file.

BufferedReader inFile = null;

PrintWriter outFile = null;

try

{

inFile = new BufferedReader(new FileReader("filename.csv"));

outFile = new PrintWriter(new FileWriter("filelines.txt"));

String readData;

System.out.println ("---OUTPUT FILE BEING PRODUCED---\n");

int[] freqs = new int[26];

while ((readData = inFile.readLine()) != null)

{

outFile.println(readData);

}

}

finally

{

System.out.println ("\n\n---PROCESSING COMPLETED---\n");

if (inFile != null)

{

inFile.close();

}

if (outFile != null)

{

outFile.close();

}

}

Can anyone offer any insight/tips in how to go about this? Thanks for reading!

Answer 1

Here is the solution if you have any doubt then please write in the comment section.

Please give feedback.

Solution: I have written comments for each line for better understanding.

I have provided two solution:

1st which is used in program is : storing frequency of uppercase and lowercase seperately using array of size 123

2nd which is commented after program is : storing frequency of uppercase and lowercase combinely in the array of length 27

import java.io.*;
public class Main
{
    //main method throws IOException because IOException is checked Exception
        public static void main(String[] args) throws IOException
        {
            //BufferedReader and PrintWriter reference variables
                BufferedReader inFile = null;
                PrintWriter outFile = null;
                try
                {
                    //open files in read and write mode respectively
                        inFile = new BufferedReader(new FileReader("filename.csv"));
                        outFile = new PrintWriter(new FileWriter("filelines.txt"));
            
            //String to store the line from file
                        String readData;
            //print msg
                        System.out.println ("---OUTPUT FILE BEING PRODUCED---\n");

            /*declare array of size 123 because ascii of a-b in the range 97-122
            and ascii of A-B is in the range 65-90, and here i am storing 
            frequency seperately for lowercase character and uppercase character
            so if you want to store frequency of both lowercase and uppercase
            together i mean (Case insensitive) then you can use modulo to store
            the frequency in the array of range 26 i will provide the same 
            implementation seperately so you can use anyone which you want*/
            
            /*Here 65 index of array is to store frequncy of Capital A and 66 
            for Capital B and so on */
                        int[] freqs = new int[123];
                        
                        /*count to store total number of character, i am counting only 
                        digits and alphabetic character*/
            int count=0;
            
            //read from file until there is data in the file
                        while ((readData = inFile.readLine()) != null)

                        {
                            //loop to iterate through all character in a single line of file 
                            for(int i=0;i<readData.length();i++)
                            {
                                /*if character is alphabetic [we are checking using ascii ]
                                then add frequency in the array*/
                                if((readData.charAt(i)>=65&&readData.charAt(i)<=90)||
                                (readData.charAt(i)>=97&&readData.charAt(i)<=122))
                                {
                                    //increment count
                                    count++;
                                    //increment frequency of particular alphabate  
                                    freqs[readData.charAt(i)]+=1;
                                }
                                //if character is digit then increment only count
                                else if(readData.charAt(i)>=48&&readData.charAt(i)<=57)
                                {
                                    count++;
                                }
                                
                            }

                                

                        }
                        //printing frequency of characters in file for your understanding
                        for(int i=65;i<=90;i++)
                        {
                            char ch=(char)i;
                            outFile.println(ch+" "+freqs[i]);
                        }
                        for(int i=97;i<=122;i++)
                        {
                            char ch=(char)i;
                            outFile.println(ch+" "+freqs[i]);
                        }
                        //printing total count
                        outFile.println("Total Count: "+count);

                }
                catch(IOException e)
                {
                    e.printStackTrace();
                }

                finally

                {

                        System.out.println ("\n\n---PROCESSING COMPLETED---\n");

                        if (inFile != null)

            {

                inFile.close();

            }

            if (outFile != null)

            {

            outFile.close();

            }
                        

                }
                System.out.println("Hello World");
        }
}


/*  This procedure is for if you want that frequency of a and A will be treated
    as same
int[] freqs = new int[27];
                        
                        /*count to store total number of character, i am counting only 
                        digits and alphabetic character*/
                        
                        /*
            int count=0;
            
            //read from file until there is data in the file
                        while ((readData = inFile.readLine()) != null)

                        {
                            //loop to iterate through all character in a single line of file 
                            for(int i=0;i<readData.length();i++)
                            {
                                /*if character is alphabetic [we are checking using ascii ]
                                then add frequency in the array*/
                                
                          /*      if((readData.charAt(i)>=65&&readData.charAt(i)<=90))
                                {
                                    //increment count
                                    count++;
                                    //here modulo 65 used so that A will have frequency at
                                    //index 1 and B will have frequency at index 2 and so on  
                                    freqs[readData.charAt(i)%65+1]+=1;
                                }
                                else if(readData.charAt(i)>=97&&readData.charAt(i)<=122)
                                {
                                    //increment count
                                    count++;
                                    //here modulo 97 used so that a will have frequency at
                                    //index 1 and b will have frequency at index 2 and so on
                                    freqs[readData.charAt(i)%97+1]+=1;
                                }
                                //if character is digit then increment only count
                                else if(readData.charAt(i)>=48&&readData.charAt(i)<=57)
                                {
                                    count++;
                                }
                                
                            }

                        

                        }
*/

Input and Output:

filename.csv

abx,Abc,ABC
cde,RTY,QWEQWEQ,XCVXCV
tytyu,WERWER,fghfgh

output file: filelines.txt

A 2
B 1
C 3
D 0
E 4
F 0
G 0
H 0
I 0
J 0
K 0
L 0
M 0
N 0
O 0
P 0
Q 3
R 3
S 0
T 1
U 0
V 2
W 4
X 2
Y 1
Z 0
a 1
b 2
c 2
d 1
e 1
f 2
g 2
h 2
i 0
j 0
k 0
l 0
m 0
n 0
o 0
p 0
q 0
r 0
s 0
t 2
u 1
v 0
w 0
x 1
y 2
z 0
Total Count: 45

If you have any type of doubts then please write in the comment section, I will feel happy to help you.

Please give feedback.

Thank You!