Thread: Returning Null

Hello once again! I need to make a program that will count the number of vowels and consonants in a string and have that number returned. The program runs, however, it always returns vowels or consonants as both being "null".

I am working off a UML and have the code essentially done, I just need to know why it is not returning a value. I have my code below, as well as the UML as an attachment. Maybe I am misinterpreting the UML? Or, more likely, something is screwed up in the countVowelsAndCons method?

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
 
package vowelcons;
 
import java.util.Scanner;
 
/**
 *
 * @author Matthew Wood
 */
public class Main {
 
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        String input;
        char selection;
 
        Scanner keyboard = new Scanner(System.in);
        System.out.println("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("\nNumber of consonants: " + vc.getNumConsonants());
                break;
                case 'd': System.out.println("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.println("Only enter a,b,c,d, or e: ");
            input = keyboard.nextLine();
            selection = input.charAt(0);
        }
        return selection;
    }
}

public class VowelCons {
    private char [] vowels;
    private char [] consonants;
    private int numVowels = 0;
    private int numCons = 0;
    private String str;
 
    public VowelCons(String string){
            string = str;
    }
 
 
    public char[] getNumConsonants() {
        return consonants;
    }
 
    public char[] getNumVowels() {
        return vowels;
    }
 
    private void countVowelsAndConsonants(){
        for (int i = 0; i < 100; i++) {
            char ch = str.charAt(i);
            if ((ch == 'a') || (ch == 'e') || (ch == 'i') || (ch == 'o') || (ch == 'u') ) {
                numVowels++;
            } 
 
            else if (Character.isLetter(ch)) {
                numCons++;
            }
    }
 
    }
}

Thanks for any help! It is greatly appreciated!

Where do you ever assign any values to the returned variables?

Norm is sending you in the right direction, so I have a question. Should we treating "Y" as a vowel or a consonant?

@aussie - "Y" is treated as a consonant.

@Norm - Are you asking if I initialized the return variables to any value? Or is that I need to assign a variable to my return variables? I'm sorry, I am just a little bit confused by the question.

Thanks for that push from both of you! However, when I do give the array values, I get something like this "[C@13caecd" returned instead of the number of vowels or consonants! Any thoughts to where I may be going wrong?

I took out the values of the array for the sake of brevity, but the returned result is the same.

public char[] getNumConsonants() {
        consonants = new char[]{};
        return consonants;
    }
 
    public char[] getNumVowels() {
        vowels = new char[]{};
        return vowels;
    }

Also if I try to declare the array in the method I get an error message. This is what I did before taking it out, just to show that I am following you.

public char[] getNumConsonants() {
        char[] = consonants;
        consonants = new char[]{};
        return consonants;
    }

@helloworld922 -- Wouldn't that array just return a string letter as opposed to a number (which is what is needed) ? It is supposed to return the number of vowels/consonants in a string.

Arrays are a little tricky. They are a kind of object. You can define an array without putting any values into it.
char[] anArray = new char[10]; // create an array with 10 slots. All ten slots will be null

anArray[0] = 'c'; // put a value into the array. now the first element has a value.

When you print an array variable, what do expect to see? Its an object with some contents. The default toString() method returns something like: "[C@13caecd" which says [= an array, C= char, @... the address in memory.

To see the contents of the array you either need to specifically index each element in it or you could use the Arrays.toString() method.

Originally Posted by Norm

char[] anArray = new char[10]; // create an array with 10 slots. All ten slots will be null

No, they'll have the value '\0'

Primitives can't be null.

db

Hmm, learn something new every day.