Question

Given java code is below, please use it!

Problem a (LA2a.java) In this assignment you are to implement a challenge-response system to protect a user's numeric PIN which they will enter via a phone. First you will be supplied a 1o-digit numeric string (the challenge) Then, a PIN will be supplied as though typed into a phone 2 A B C DEF GHI J KL M NO PQRS TUV WXYZ So, "AGOT" would signify PIN 2468. To compute a response, substitute each PIN digit with the corresponding challenge digit. For example, assume this challenge (indexes shown for convenience) SEQUENCE 3 INDEX 2 2 2 0 2 8 If supplied ΆGOT' via phone (PIN: 2468), you would respond 3121 (the value at index 2, followed by index 4,...). Note that the PIN can be any length (1 or more characters). Also note that if the challenge has repeated digits, the PIN itself is protected because many input PINs could have the same response (and future communications can use a different challenge) You will need to validate the challenge (10 all-digit characters) and the PIN (all digits) and then output the response. For example:

import java.util.Scanner;

public class LA2a {
  
   /**
   * Number of digits in a valid value sequence
   */
   public static final int SEQ_DIGITS = 10;
  
   /**
   * Error for an invalid sequence
   * (not correct number of characters
   * or not made only of digits)
   */
   public static final String ERR_SEQ = "Invalid sequence";
  
   /**
   * Error for an invalid pin
   * (not made entirely of
   * uppercase letters)
   */
   public static final String ERR_PIN = "Invalid PIN";
  
   /**
   * Converts an uppercase letter
   * to the corresponding number on
   * a standard phone...
   *
   * 1:
   * 2: ABC
   * 3: DEF
   *
   * 4: GHI
   * 5: JKL
   * 6: MNO
   *
   * 7: PQRS
   * 8: TUV
   * 9: WXYZ
   *
   * *:
   * 0: +
   * #:
   *
   * @param c assumed to be uppercase letter
   * @return corresponding phone number
   */
   public static int letterToPhone(char c) {
       return 0; // replace with your code
   }
  
   /**
   * Takes an input PIN and produces a response
   * via first converting each character via phone
   * number, then using that as an index
   * to a value sequence
   *
   * @param pin input PIN (assumed to be uppercase letters)
   * @param values input value sequence
   * @return response
   */
   public static int[] getResponse(String pin, int[] values) {
       int[] response = new int[pin.length()];
      
       // write your code here
      
       return response;
   }
  
   /**
   * Returns true if the length of the
   * input string is equal to the input
   * parameter
   *
   * @param s input string
   * @param k length to check
   * @return true if length of string
   */
   public static boolean stringIsKDigits(String s, int k) {
       return false; // replace with your code
   }
  
   /**
   * Returns true if all the characters
   * in the input string are '0' through '9'
   *
   * @param s input string
   * @return true if all characters in s are digits
   */
   public static boolean allDigits(String s) {
       return false; // replace with your code
   }
  
   /**
   * Returns true if all the characters
   * in the input string are 'A' through 'Z'
   *
   * @param s input string
   * @return true if all characters are uppercase letters
   */
   public static boolean allUppercaseLetters(String s) {
       return false; // replace with your code
   }
  
   /**
   * Converts a string of digits to an
   * array of integers (e.g. "12" -> {1, 2})
   *
   * Assumes string is comprised of only digits!
   *
   * @param s digit string
   * @return corresponding integer array
   */
   public static int[] digitStringToIntArray(String s) {
       return null; // replace with your code
   }
  
   /**
   * Returns how many times a value
   * occurs within an array
   *
   * @param value needle
   * @param values haystack
   * @return how many times the needle occurs in the haystack
   */
   public static int countValues(int value, int[] values) {
       return 0; // replace with your code
   }
  
   /**
   * Returns how many ways the response could have been
   * produced from a given value sequence
   *
   * @param response output
   * @param values value sequence
   * @return how many PINs could have produced the same response given the value sequence
   */
   public static int numPossible(int[] response, int[] values) {
       return 0; // replace with your code
   }
  
   /**
   * Inputs a value sequence and PIN,
   * outputs challenge response
   *
   * @param args command-line arguments, ignored
   */
   public static void main(String[] args) {
       @SuppressWarnings("resource")
       final Scanner in = new Scanner(System.in);
      
       System.out.printf("Enter value sequence: ");
       final String seq = in.nextLine();
      
       System.out.printf("Enter PIN: ");
       final String pin = in.nextLine();
      
       // write your code here
   }

}

Answer 1

Explanation::

• Code in JAVA is given below
• Please read comments for better understanding of the code
• Screenshots of the OUTPUT are given at the end of the code

Code in JAVA::

import java.util.Scanner;

public class LA2a {

   /**
   * Number of digits in a valid value sequence
   */
   public static final int SEQ_DIGITS = 10;

   /**
   * Error for an invalid sequence
   * (not correct number of characters
   * or not made only of digits)
   */
   public static final String ERR_SEQ = "Invalid sequence";

   /**
   * Error for an invalid pin
   * (not made entirely of
   * uppercase letters)
   */
   public static final String ERR_PIN = "Invalid PIN";

   /**
   * Converts an uppercase letter
   * to the corresponding number on
   * a standard phone...
   *
   * 1:
   * 2: ABC
   * 3: DEF
   *
   * 4: GHI
   * 5: JKL
   * 6: MNO
   *
   * 7: PQRS
   * 8: TUV
   * 9: WXYZ
   *
   * *:
   * 0: +
   * #:
   *
   * @param c assumed to be uppercase letter
   * @return corresponding phone number
   */
   public static int letterToPhone(char c) {
       if(c=='A' || c=='B' || c=='C') {
           return 2;
       }else if(c=='D' || c=='E' || c=='F') {
           return 3;
       }else if(c=='G' || c=='H' || c=='I') {
           return 4;
       }else if(c=='J' || c=='K' || c=='L') {
           return 5;
       }else if(c=='M' || c=='N' || c=='O') {
           return 6;
       }else if(c=='P' || c=='Q' || c=='R' || c=='S') {
           return 7;
       }else if(c=='T' || c=='U' || c=='V') {
           return 8;
       }else if(c=='W' || c=='X' || c=='Y' || c=='Z') {
           return 9;
       }else if(c=='+') {
           return 0;
       }
       return 0;
   }

   /**
   * Takes an input PIN and produces a response
   * via first converting each character via phone
   * number, then using that as an index
   * to a value sequence
   *
   * @param pin input PIN (assumed to be uppercase letters)
   * @param values input value sequence
   * @return response
   */
   public static int[] getResponse(String pin, int[] values) {
       int[] response = new int[pin.length()];
       /**
       * Running through the String pin and
       * calling letterToPhone() method for each char of String pin
       * And whatever the integer value is returned by letterToPhone(),
       * It is used as index for values[] array and whatever the value is
       * present there, It is stored in response
       *
       * */
       for(int i=0;i<pin.length();i++) {
           response[i]=values[letterToPhone(pin.charAt(i))];
       }
       return response;
   }

   /**
   * Returns true if the length of the
   * input string is equal to the input
   * parameter
   *
   * @param s input string
   * @param k length to check
   * @return true if length of string
   */
   public static boolean stringIsKDigits(String s, int k) {
       return s.length()==k;
   }

   /**
   * Returns true if all the characters
   * in the input string are '0' through '9'
   *
   * @param s input string
   * @return true if all characters in s are digits
   */
   public static boolean allDigits(String s) {
       /**
       * for loop traverse through each character of string s
       * and check if each char is digit or not.
       * if any char is not digit then false is returned
       * */
       for(int i=0;i<s.length();i++) {
           if(!Character.isDigit(s.charAt(i))) {
               return false;
           }
       }
       return true;
   }

   /**
   * Returns true if all the characters
   * in the input string are 'A' through 'Z'
   *
   * @param s input string
   * @return true if all characters are uppercase letters
   */
   public static boolean allUppercaseLetters(String s) {
       /**
       * for loop traverse through each character of string s
       * and check if each char is upper case or not.
       * if any char is not upper case then false is returned
       * */
       for(int i=0;i<s.length();i++) {
           if(!Character.isUpperCase(s.charAt(i))) {
               return false;
           }
       }
       return true;
   }

   /**
   * Converts a string of digits to an
   * array of integers (e.g. "12" -> {1, 2})
   *
   * Assumes string is comprised of only digits!
   *
   * @param s digit string
   * @return corresponding integer array
   */
   public static int[] digitStringToIntArray(String s) {
       int digitArray[]=new int[s.length()];
       for(int i=0;i<s.length();i++) {
           digitArray[i]=Character.getNumericValue(s.charAt(i));
       }
       return digitArray; // replace with your code
   }

   /**
   * Returns how many times a value
   * occurs within an array
   *
   * @param value needle
   * @param values haystack
   * @return how many times the needle occurs in the haystack
   */
   public static int countValues(int value, int[] values) {
       int count=0;
       for(int i=0;i<values.length;i++) {
           if(values[i]==value) {
               count++;
           }
       }
       return count;
   }

   /**
   * Returns how many ways the response could have been
   * produced from a given value sequence
   *
   * @param response output
   * @param values value sequence
   * @return how many PINs could have produced the same response given the value sequence
   */
   public static int numPossible(int[] response, int[] values) {
       int answer=1;
       for(int i=0;i<response.length;i++) {
           answer=answer*countValues(response[i],values);
       }
       return answer;
   }

   /**
   * Inputs a value sequence and PIN,
   * outputs challenge response
   *
   * @param args command-line arguments, ignored
   */
   public static void main(String[] args) {
       @SuppressWarnings("resource")
       final Scanner in = new Scanner(System.in);

       System.out.printf("Enter value sequence: ");
       final String seq = in.nextLine();

       System.out.printf("Enter PIN: ");
       final String pin = in.nextLine();
      
      
       if(!stringIsKDigits(seq,SEQ_DIGITS) || !allDigits(seq)) {
           System.out.println(ERR_SEQ);
       }else if(!allUppercaseLetters(pin)) {
           System.out.println(ERR_PIN);
       }else {
           int values[]=digitStringToIntArray(seq);
           int response[]=getResponse(pin,values);
           System.out.print("Response: ");
           for(int i=0;i<response.length;i++) {
               System.out.print(response[i]);
           }
           System.out.println();
       }
   }

}

OUTPUT::

TEST CASE 1::

Enter value sequence: 12345 Enter PIN: HELLO Invalid sequence

TEST CASE 2::

<terminatdLAa ava Application] C:Program File Enter value sequence: 0.16767265652 Enter PIN: HELLO Invalid sequence

TEST CASE 3::

<terminated> LA2a [Java Application] C:Progran Enter value sequence: 0123456789 Enter PIN: Hello Invalid PIN

TEST CASE 4::

<terminated> LA2a [Java Application] C:Program Files Enter value sequence: 0123456789 Enter PIN: HELLO Response: 43556

TEST CASE 5::

<terminated> LA2a [Java Application] CProgran Enter value sequence: 3231132213 Enter PIN: AGOT Response: 3121

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