Why isn' this counting vowels?

Question

I need to count the vowels but this is always returning 0?

public static int numVowel(String s) {
  int count = 0,x;
  for(x = 0; x<s.length();x++)
    if (x=='a' || x=='e' || x=='i' || x=='o' || x=='u' || x=='A' || x=='E' || x=='I' || x=='O' || x=='U')
    count++;
  return count;
}

`x` is only an index into string `s`. You must retrieve the character at position `x` and compare it with the vowels. — Michael Butscher, Apr 03 '19 at 03:08
What do you think that `x` is? What is its type? When is it set and to what value is it set? — Jonathon Reinhart, Apr 03 '19 at 03:09

score 0 · Answer 1 · answered Apr 03 '19 at 03:08

0

You are comparing your counter/index against char literals.

Instead, you should retrieve the character at the indexed position against these literals! See Get string character by index - Java here for how to do that!

answered Apr 03 '19 at 03:08

GhostCat

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score 0 · Answer 2 · edited Apr 03 '19 at 03:10

0

It should be s.charAt(x) == 'a' instead of x == 'a'. You should check the character at the given index.

edited Apr 03 '19 at 03:10

shmosel

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answered Apr 03 '19 at 03:09

Urmil Parikh

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score 0 · Answer 3 · answered Apr 03 '19 at 03:10

0

You don't want to check the value of x; you want to check the value of the character at position x. You can do this with s.charAt(x).

answered Apr 03 '19 at 03:10

Adam P

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Elliott Frisch · Answer 4 · 2019-04-04T04:57:15.030

Because x is your index (not the characters from s). Also, always use braces (even when they're optional). To fix it with your current approach, do something like

public static int numVowel(String s) {
    int count = 0;
    for (int i = 0; i < s.length(); i++) {
        char x = s.charAt(i);
        if (x == 'a' || x == 'e' || x == 'i' || x == 'o' || x == 'u' || x == 'A' || x == 'E' || x == 'I' || x == 'O'
                || x == 'U') {
            count++;
        }
    }
    return count;
}

But I would prefer something like

public static int numVowel(String s) {
    int count = 0;
    for (char ch : s.toLowerCase().toCharArray()) {
        if ("aeiou".indexOf(ch) > -1) {
            count++;
        }
    }
    return count;
}

Or use a regular expression to remove everything that isn't a vowel from the input String and then return the length of that. Like,

public static int numVowel(String s) {
    return s.toLowerCase().replaceAll("[^aeiou]", "").length();
}

If you need to invoke this many many times then the cost of calling String.toLowerCase() is not insignificant; and you might compile that regex into a Pattern.

private static Pattern _PATTERN = Pattern.compile("[^aeiouAEIOU]");
public static int numVowel(String s) {
    return _PATTERN.matcher(s).replaceAll("").length();
}

Why isn' this counting vowels?

4 Answers4