can you please comment steps so i can follow along, and post screenshots. please

Question

can you please comment steps so i can follow along, and post screenshots. please and thank you.

Program Submission Instructions: You must submit your source code file The source code file must be submitted in Webcourses from the assignment page All source code must be in exactly one file of type c, cpp, or java CIS 3360 - Security in Computing Summer 2018 HW #2 Checksum (100 points) In this assignment you'll write a program that calculates the checksum for the text in a file. Your program wil take two command line parameters. The first parameter will be the name of the input file for calculating the checksum. The second parameter will be for the size of the checksum (8, 16 or 32 bits). The program must generate output to the console (terminal) screen as specified below Command Line Parameters 1. Your program must compile and run from the command line. 2. The program executable must be named "checksum" (all lower case, no spaces or file extension) Input the required file names as command line parameters. Your program may NOT prompt the user to enter the file names. The first parameter must be the name of the file used for calculating the checksum, as described below. The second parameter must be the size, in bits, of the checksum. The sample run command near the end of this document contains an example of how the parameters will be entered. 3. 4. Your program should open the two files, echo the processed input to the screen, make the necessary calculations, and then output the ciphertext to the console (terminal) screen in the format described below.

Explanation / Answer

import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Arrays;

public class checksum {

    public static void main(String[] args) {
        int checkSumSize = 0, characterCount = 0, checkSumResult = 0;
        String input = null;
        byte[] fileBytes;

        if (args.length < 2 || !Character.isDigit(args[1].charAt(0)) || !validBitSize(Integer.parseInt(args[1]))) {
            if (!Character.isDigit(args[1].charAt(0)) || !validBitSize(Integer.parseInt(args[1])))
                System.err.print(" Valid checksum sizes are 8, 16, or 32 ");
            else
                System.err.println(" Please provide the proper parameters. " +
                        "First Parameter is the input file name, second is the size of the checksum. ");
            System.exit(1);
        }

        try {
            input = readFileAsString(args[0]);
        } catch (Exception e) {
            e.printStackTrace();
        }

        if (input != null){
            switch (Integer.parseInt(args[1])) {
                case 8:
                    checkSumSize = 8;
                    fileBytes = getAdjustedByteArray(input, checkSumSize);
                    characterCount = fileBytes.length;
                    checkSumResult = checksum8(fileBytes);
                    break;
                case 16:
                    checkSumSize = 16;
                    fileBytes = getAdjustedByteArray(input, checkSumSize);
                    characterCount = fileBytes.length;
                    checkSumResult = checksum16(fileBytes);
                    break;
                case 32:
                    checkSumSize = 32;
                    fileBytes = getAdjustedByteArray(input, checkSumSize);
                    characterCount = fileBytes.length;
                    checkSumResult = checksum32(fileBytes);
                    break;
                default:
                    System.err.print("Valid checksum sizes are 8, 16, or 32 ");
                    System.exit(1);
                    break;
            }
            System.out.printf(" %s %2d bit checksum is %8x for all %4d chars ",
                    formattedStringOutput(getAdjustedString(input, checkSumSize)), checkSumSize, checkSumResult, characterCount);
        }
    }

    // Checksum 8-Bit

    private static int checksum8(byte[] data) {
        int check = 0;

        for (byte b : data)
            check += b;

        return check & 0xFF;
    }

    // Checksum 16-bit

    private static int checksum16(byte[] data) {
        int check = 0;

        for (int i = 0; i <= data.length - 2; i += 2)
            check += ((data[i] << 8) | (data[i + 1] & 0xFF));

        return check & 0xFFFF;
    }

    // Checksum 32-bit
  
    private static int checksum32(byte[] data) {
        int check = 0;

        for (int i = 0; i < data.length; i += 4)
            check += ((data[i] << 24) | (data[i + 1] << 16) | (data[i + 2] << 8) | (data[i + 3])) & 0xffffffffL;

        return check;
    }

  
    private static String readFileAsString(String fileName) throws Exception {
        String data;
        data = new String(Files.readAllBytes(Paths.get(fileName)));
        return data;
    }

    private static String formattedStringOutput(String output) {
        StringBuilder res = new StringBuilder();
        for (int i = 0; i < output.length(); i++) {
            if (i > 0 && i % 80 == 0)
                res.append(" ");
            res.append(output.charAt(i));
        }
        return res.toString();
    }

    private static byte[] getAdjustedByteArray(String in, int bit) {
        int originalSize = in.getBytes().length, newSize;

        newSize = originalSize + getPadding(originalSize, bit);
        byte[] temp = new byte[newSize];

        for (int i = 0; i < originalSize; i++) {
            temp[i] = (byte) in.charAt(i);
        }

        if (getPadding(originalSize, bit) > 0) {
            for (int j = originalSize; j < newSize; j++) {
                temp[j] = 88;
            }
        }
        return temp;
    }

    private static String getAdjustedString(String in, int bit) {
        int originalSize = in.getBytes().length, newSize;
        StringBuilder builder = new StringBuilder();
        newSize = originalSize + getPadding(originalSize, bit);

        for (int i = 0; i < originalSize; i++) {
            builder.append(in.charAt(i));
        }

        if (getPadding(originalSize, bit) > 0) {
            for (int j = originalSize; j < newSize; j++) {
                builder.append("X");
            }
        }

        return builder.toString();
    }

    private static boolean validBitSize(int bit) {
        int[] validBits = {8, 16, 32};
        return Arrays.stream(validBits).anyMatch(i -> i == bit);
    }

  
    private static int getPadding(int lengthOriginal, int bit) {
        int a = lengthOriginal;
        int b = bit == 32 ? 4 : 2;
        int c = 0;
        while (a % b != 0) {
            a = a + 1;
            c++;
        }
        return bit > 8 ? c : 0;
    }

}

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