java iterative to recursive 2 nested for loop

Question

I would like to check whether a string contains a sub list.
For example, str1 = "qwertyuiop" and str2 = "tyu" returns true.
I have written an iterative method.

public static boolean checkString(String str1, String str2) {
    for (int i=0; i<str2.length(); i++) {
        int j = 0;
        for (; j<str1.length()&& str1.charAt(j)!=str2.charAt(i); j++) {

        }
        if (j== str1.length())
            return false;
    }
    return true;    
}

I am trying changing it to recursive method but not sure how as there are two nested for loops. Thank you in advance.

@sam_eera @Tyler this is just an example of using nested for loop as I want to see how recursion will work when there's more than one loop. — user2875021
– user2875021, Commented Oct 20, 2014 at 4:20

Elliott Frisch · Accepted Answer · 2014-10-20 04:14:01Z

3

I suggest you focus on other activities. Java already includes a function to do what you are implementing, and that is String.contains(CharSequence) like

if (str1.contains(str2)) { // <-- wherever you would have called "checkString"
  // ...
}

answered Oct 20, 2014 at 4:14

Elliott Frisch

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Ankur Singhal · Accepted Answer · 2014-10-20 04:15:19Z

1

public class Test {

    public static void main(String[] args) {
        System.out.println(isSubstring("ankur", "ku"));
    }

    public static boolean isSubstring(String str1, String str2) {
        if ((str1 == null) || (str2 == null) || str1.isEmpty()) {
            return false;
        } else if (str1.startsWith(str2)) {
            return true;
        } else {
            return isSubstring(str1.substring(1), str2);
        }
    }
}

answered Oct 20, 2014 at 4:15

Ankur Singhal

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