Question

I changed my code as Dan suggested i can compile the program now, however, whatever the input is, the result is always 2. i put the second part of this program below the new code. please help.

Here’s the NEW code.

    public class VowelCons 
        {
    private final String str;
    private final int totalConsonants;
    private final int totalVowels;

        public VowelCons(final String s) 
    {
             this.str = s;
                int totalConsonants = 0;
                int totalVowels = 0;
                if (null != s) 
        {
                    for (final char c : s.toCharArray()) 
            {
                                switch (c) 
                    {
                                        case 'A':
                                        case 'a':
                                        case 'E':
                                        case 'e':
                                        case 'I':
                                        case 'i':
                                        case 'O':
                                        case 'o':
                                        case 'U':
                                        case 'u':

                        totalVowels++;
                                            break;

                        default:

                        if (Character.isLetter(c)) 
                        {
                                                    totalConsonants++;
                                            }
                                            break;
                                    }
                        }
                }
            this.totalConsonants = totalConsonants;
            this.totalVowels = totalVowels;
        }


    public String getString() 
    {
             return str;
    }

    public int getNumConsonants() 
    {
                return this.totalConsonants;
    }

    public int getNumVowels() 
    {
                return this.totalConsonants;
    }
}

there’s another part of this program which gets the user’s input and passes it to this class.
Here’s the code. [this part cannot be changed according to the regulations]

    import java.util.Scanner;

    public class VowelConsCounter
    {
        public static void main(String[] args)
        {
         String input;        // User input
         char selection;      // Menu selection

         Scanner keyboard = new Scanner(System.in);

         System.out.print("Enter a string: ");
         input = keyboard.nextLine();

         VowelCons vc = new VowelCons(input);

        do
        {
          selection = getMenuSelection();

          switch(Character.toLowerCase(selection))
          {
            case 'a' :  System.out.println("\nNumber of vowels: " +
                        vc.getNumVowels());
                        break;
            case 'b' :  System.out.println("\nNumber of consonants: " +
                        vc.getNumConsonants());
                        break;
            case 'c' :  System.out.println("\nNumber of vowels: " +
                        vc.getNumVowels());
                        System.out.println("Number of consonants: " +
                        vc.getNumConsonants());
                        break;
            case 'd' :  System.out.print("Enter a string: ");
                        input = keyboard.nextLine();
                        vc = new VowelCons(input);
         }

      } while (Character.toLowerCase(selection) != 'e');

   }

   public static char getMenuSelection()
   {
      String input;     
      char selection;   

      Scanner keyboard = new Scanner(System.in);

      System.out.println("a) Count the number of vowels in the string.");
      System.out.println("b) Count the number of consonants in the string.");
      System.out.println("c) Count both the vowels and consonants in the string.");
      System.out.println("d) Enter another string.");
      System.out.println("e) Exit the program.");

      input = keyboard.nextLine();
      selection = input.charAt(0);

      while (Character.toLowerCase(selection) < 'a' || Character.toLowerCase(selection) > 'e')
      {
         System.out.print("Only enter a, b, c, d, or e: ");
         input = keyboard.nextLine();
         selection = input.charAt(0);
      }

      return selection;
   }
}

Answer 1

You’re getting a NullPointerException because you are not initializing the instance variable result.

I would recommend using the following:

public class VowelCons {
    private final String str;
    private final int totalConsonants;
    private final int totalVowels;

    public VowelCons(final String s) {
        this.str = s;
        int totalConsonants = 0;
        int totalVowels = 0;
        if (null != s) {
            for (final char c : s.toCharArray()) {
                switch (c) {
                    case 'A':
                    case 'a':
                    case 'E':
                    case 'e':
                    case 'I':
                    case 'i':
                    case 'O':
                    case 'o':
                    case 'U':
                    case 'u':
                        totalVowels++;
                        break;
                    default:
                        if (Character.isAlphabetic(c)) {
                            totalConsonants++;
                        }
                        break;
                }
            }
        }
        this.totalConsonants = totalConsonants;
        this.totalVowels = totalVowels;
    }

    public String getString() {
        return str;
    }

    public int getTotalConsonants() {
        return this.totalConsonants;
    }

    public int getTotalVowels() {
        return this.totalConsonants;
    }

    public String toString() {
        return (null == str ? "" : str) + " [consonants=" + totalConsonants + ", vowels=" + totalVowels + "]";
    }

    public static void main(final String[] args) {
        for (final String arg : args) {
            final VowelCons vc = new VowelCons(arg);
            System.out.println(vc.toString());
        }
    }
}

This would, for example, output:

$ java VowelCons foo BaR "Lady GODIVA"
foo [consonants=1, vowels=2]
BaR [consonants=2, vowels=1]
Lady GODIVA [consonants=6, vowels=4]

Here are some points this example should help you learn:

1. Local variables may hide instance variables (see [1] and [2]).
2. Use this to reference instance variables (see [1]). You should always reference instance variables using this, which prevents accidentally hiding it when you make future code changes and allows IDEs to provide context sensitive suggestions that only contain instance members.
3. Handle null Strings passed to the constructor.
4. Use switch to simplify the logic and reduce redundant code in if-else logic.
5. Check for lower-case and upper-case vowels.
6. Ignore non-alphabetic characters in the vowel/consonant counts.
7. Implement a custom toString().