/** * Returns a subset of the larger playlist as an ArrayList of songs that * have the same genre. * @param song * @precondition the playlist is not empty. * @precondition the passed-in element is not null * @return an array list of all songs with the same genre. * * 1. if the playlist array is empty or the passed-in element is null, return null. * 2. otherwise: * a. create an ArrayList with generic type E to hold songs. * a. loop through the entire playlist array * i. if the current song has the same genre as what was passed in, * add it to the ArrayList. * 3. return the ArrayList. */ public ArrayList createSmartPlaylist(E song);