Java boolean recursive method for Strings count

Question

I have to use recursion to implement a boolean method. No any for loop is allowed. The code I wrote turns out the right answer as given. However, it is not correct yet. Is there any good suggestion? Thanks!

public class RecusiveMethod {

    public static void main ( String[] args ) {
        System.out.println( "True: " + isWordCountsRight( "ccowcow", "cow", 2 ) );
        System.out.println( "True: " + isWordCountsRight( "kayakayakaakayak", "kayak", 3 ) );
    }


    public static boolean isWordCountsRight( String str, String word, int n ) {
        if ( n == 0 ) return true;

        if ( str.substring( 0, word.length() ).equals( word ) ) {
            return isWordCountsRight( str.substring( 1 ), word, n - 1 );
        }

        return isWordCountsRight( str.substring( 1 ), word, n );
    }
}

Do you expect 2 or 3 in the second case? Match with overlapping or not? — blafasel
– blafasel, Commented Feb 27, 2016 at 1:28
note that you never return false - guess that is your problem here — MartinS
– MartinS, Commented Feb 27, 2016 at 1:40

Maljam · Accepted Answer · 2016-02-27 01:38:53Z

1

You could also do it like so:

public static boolean isWordCountsRight(String str, String word, int n) {
if (n == 0) return true;

int index = str.indexOf(word);

if (index != -1) {
    return isWordCountsRight(str.substring(index+1), word, n - 1);
} else {
    return false;
}

edited Feb 27, 2016 at 1:38

answered Feb 27, 2016 at 1:29

Maljam

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3 Comments

blafasel Over a year ago

That's without overlapping. You'll get 2 in the second case.

Maljam Over a year ago

You're right, I got too greedy by trying to save potentially redundant steps. But that's an easy fix, just replace word.length() by 1

xh2000 Over a year ago

Thanks to all your suggestions!

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