Question

VIII JAVA ASSIGNMENT

Phone numbers and PIN codes can be easier to remember when you find words that spell out the number on a standard phone pad. For example, instead of remembering the combination

5282, you can just think of JAVA. Write a recursive method that given a number, yields all possible spellings (which may or may not be real words). Please use the file included as a starting point.

Possible testing values are:

5282

26678837

7764726

Answer 1

`Hey,

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import java.util.Scanner;

public class PinWordEnumerator {

public static void main(String[] args) {

Scanner scanner = new Scanner(System.in);

System.out.print("Enter pin number: ");

String num = scanner.nextLine();

System.out.println();

System.out.printf("The keypad encodings for %s are:%n", num);

enumerateWords(num);

}

/**

* method to return a character array containing all possible keypad

* encodings for a digit in a standard phone

*/

static char[] getKeysForButton(int n) {

switch (n) {

case 0:

return new char[] { ' ' }; //returning only space

case 1:

return new char[] { '.' }; //returning only dot

case 2:

//button 2 contains A, B and C keys

return new char[] { 'A', 'B', 'C' };

case 3:

return new char[] { 'D', 'E', 'F' };

case 4:

return new char[] { 'G', 'H', 'I' };

case 5:

return new char[] { 'J', 'K', 'L' };

case 6:

return new char[] { 'M', 'N', 'O' };

case 7:

return new char[] { 'P', 'Q', 'R', 'S' };

case 8:

return new char[] { 'T', 'U', 'V' };

case 9:

return new char[] { 'W', 'X', 'Y', 'Z' };

}

return null;

}

/**

* method to enumerate words

*

* @param num

* - String containing pin numbers, assuming it has only numbers

*/

static void enumerateWords(String num) {

/**

* calling the recursive method to perform the enumeration

*/

if (num != null)

enumerateWords(num, "");

}

/**

* the main method which performs the recursion

*

* @param num

* - current number

* @param text

* - text containing converted spellings

*/

static void enumerateWords(String num, String text) {

if (num.length() == 0) {

// base case, displaying the text

System.out.println(text);

} else {

// finding the digit at 0th position

int digit = num.charAt(0) - '0';

// finding possible phone keys for this digit

char letters[] = getKeysForButton(digit);

if (letters != null) {

// looping through all possible keys

for (int i = 0; i < letters.length; i++) {

/**

* appending the current letter to the text and calling the

* recursive method also neglecting the first letter of

* current 'num' string

*/

enumerateWords(num.substring(1), text + letters[i]);

}

}

}

}

}

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Thanks.