Collection operations for Java (intersection, set, difference) collation

/**
* Find the difference set of LS to LS2, that is, LS, but not in the LS2
*
* @param ls
* @param LS2
* @return
*/
public static list diff (list ls, list ls2) {
List List = new ArrayList (arrays.aslist (New Object[ls.size ()));
Collections.copy (list, LS);
List.removeall (LS2);
return list;
}

   /**
     * Find the intersection of 2 sets
     *
      * @param ls
     * @param ls2
     * @return
      */
    public static list intersect (list ls, list ls2) {
         list = new ArrayList (arrays.aslist (New Object[ls.size ()));
        collections.copy (list, LS);
        List.retainall (LS2);
        return list;
   }

/**
* Find a set of 2 sets
*
* @param ls
* @param LS2
* @return
*/
public static list Union (list ls, list ls2) {
List List = new ArrayList (arrays.aslist (New Object[ls.size ()));
Collections.copy (list, LS);//Copy the value of LS to the list
List.removeall (LS2);
List.addall (LS2);
return list;
}

Collection operations for Java (intersection, set, difference) collation