Sample.java

/*   Created by IntelliJ IDEA.
 *   Author: Kshitij Varshney (kshitijvarshne1)
 *   Date: 16-May-21
 *   Time: 3:06 PM
 *   File: Sample.java
 */

public class Sample {


    public static void main(String[] args) {
        String[] s = {"ab", "aab", "xyz", "axb"};
        System.out.println(countSpecialString(s));
    }

    static int countSpecialString(String[] s) {
        int ans = 0;
        for (String i : s) {
            if ((check(i) == true)) {
                ans++;
            }
        }
        return ans;
    }

    private static boolean check(String s) {
        for (int i = 0; i < s.length(); i++) {
            if (s.charAt(i) != 'a') {
                if (s.charAt(i) != 'b') {
                    return false;
                }
            }
        }
        if(s.contains("b")==false){
            return false;
        }
        if(s.contains("a")==false){
            return false;
        }
        return true;
    }
}