Chapter 12, Problem 3E

Explanation of Solution

Creating “CharacterFrequency.java”:

• Import required package.
• Define “CharacterFrequency” class.
  • Define main function.
    • Create array for digit count using “ArrayList”.
    • Initialize the digit counts.
    • Create object for scanner class.
    • Prompt statement for telephone number.
    • Read the telephone number from user.
    • Compute the count of each character in the telephone number using “for” loop.
      • Define each character in telephone number.
      • Performs “switch” case.
        • If the digit character is “0”, then increment the count of character “0” using “set” and “get” method
        • If the digit character is “1”, then increment the count of character “1”.
        • If the digit character is “2”, then increment the count of character “2”.
        • If the digit character is “3”, then increment the count of character “3”.
        • If the digit character is “4”, then increment the count of character “4”.
        • If the digit character is “5”, then increment the count of character “5”.
        • If the digit character is “6”, then increment the count of character “6”.
        • If the digit character is “7”, then increment the count of character “7”.
        • If the digit character is “8”, then increment the count of character “8”.
        • If the digit character is “9”, then increment the count of character “9”.
      • Prompt statement for count of each digit.
      • Display the count of each digit using “for” loop.
        • Display the count by using “get” method.
      • Display count of each digit.

Program:

The below java program is used to compute the count of each digit in a telephone number using “ArrayList”.

“CharacterFrequency.java”

//Import required package

import java.util.*;

//Define "CharacterFrequency" class

public class CharacterFrequency

{

    //Define main function

    public static void main(String[] args)

    {

/* Create array for digit count using "ArrayList" */

ArrayList<Integer> digit_count = new ArrayList<Integer>();

        //Initialize the digit counts

        for(int i = 0; i < 10; i++)

        {

            digit_count.add(0);

        }

        //Create object for scanner class

        Scanner reader = new Scanner(System.in);

        //Prompt statement for user

        System.out.print("Enter a telephone number: ");

        //Read the telephone number from user

        String telephoneNumber = reader.next();

/* Compute the count of each character in the telephone number */

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

        {

/* Define each character in telephone number */

Character digit = telephoneNumber.charAt(i);

            //Performs "switch" case

            switch(digit)

            {

/* If the digit character is "0", then */

                case '0':

/* Increment the count of character '0' by using "set" and "get" method */

digit_count.set(0, digit_count.get(0)+1);

                    break;

/* If the digit character is "1", then */

                case '1':

/* Increment the count of character '1' */

digit_count...