Thread: Recursive Method to count vowel

public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.print("Enter a string: ");
String word = input.nextLine();
int i = 0, count = 0;
checkVowel(word, i, word.length()-1, count);
}

public static void checkVowel(String word, int start, int last, int count) {
if (start == last)
{
System.out.println("Total number of vowel is " + count);
}
else
{
if (word.charAt(start) == 'a' || word.charAt(start) == 'e' || word.charAt(start) == 'i' ||
word.charAt(start) == 'o' || word.charAt(start) == 'u') {
count++;
}
checkVowel(word, start++, last, count);
}
}


this is my code, but somehow i gt "Exception in thread "main" java.lang.StackOverflowError" , can anyone help find what's the problem??

public static void checkVowel(String word, int i, int last, int count) {
        if (i == last)
        {
            System.out.println("Total number of vowel is " + count);
        }
        else
        {  
           [B] i++;[/B]
            if (word.charAt(i) == 'a' || word.charAt(i) == 'e' || word.charAt(i) == 'i' ||
                word.charAt(i) == 'o' || word.charAt(i) == 'u') {
                count++;    
            }
            checkVowel(word, i, last, count);
        }           
    }

Thx for the hints..... sorry about the highlight, will keep it in mind.......

The problem lies in the recursive function, which must return something to get the previous level where it was invoked. Pleaes try the following:
public class RecursiveFunctionTest {

private static final String VOWELS = "aeiouAEIOU";

public static int checkVowels(String word, int start, int end, int count){
if(start >= end){
return count;
}
else{
if(VOWELS.indexOf(word.charAt(start)) != -1)
count++;
}

return checkVowels(word, ++start, end, count);
}

public static void main(String[] args){
Scanner input = new Scanner(System.in);
System.out.println("Enter a String: ");
String word = input.nextLine();
int count = 0;
count = checkVowels(word, 0, word.length()-1, count);
System.out.println("The total number of vowels is " + count);
}
}

No, the recursive function mustn't return a value in order to terminate. For example, this function is OK:

    public static void f(int x, int term) {
        if(x >= term) {}
        else {
            System.out.println(x + " " + term);
            f(x + 1, term);
        }
    }

StackOverflowException means, that the function can't terminate. Let's have a look at the termination condition:

        if (i == last)
        {
            System.out.println("Total number of vowel is " + count);
        }

The function terminates only when i == last. I suspect, that at some point you may erroneously call the function with i > last. In this case function will never terminate, because i increases from call to call. Try "i >= last" termination condition instead of "i == last".

Return a value or not does not matter for a recursive function indeed. The core part is to terminate it. So I agree with you that something is wrong with the termination condition. So in my example, I used ">=" instead.