נתונות הפעולות what, why ו-whyHelp:

public static boolean what(String s, char c, int k)
{
    if(k == 0 && s.length()==0) return true;
    if(s.length() == 0) return false;
    if(k < 0 ) return false;
    if(s.charAt(0)== c) return what(s.substring(1),c, k-1);
    return what(s.substring(1),c, k);
}
public static boolean why(char[] arr, String s)
{
    return whyHelp(arr, s, 0);
}
public static boolean whyHelp(char[] arr, String s, int k)
{
    if(k == arr.length) return true;
    if(!what(s, arr[k], k+1)) return false;
    return whyHelp(arr, s, k+1);
}