question: public static int countOccurrencesOf ( String str , String sub ) { if ( str == null || sub == null || str . length ( ) == 0 || sub . length ( ) == 0 ) { return 0 ; } int count = 0 ; int pos = 0 ; int idx ; while ( ( idx = str . indexOf ( sub , pos ) ) != - 1 ) { ++ count ; pos = idx + sub . length ( ) ; } return count ; }
target:  Count the occurrences of the substring in string s.