Solution for Java 8 based on java.util.Comparator.comparing(...):

Comparator<String> c = Comparator.comparing(String::toString);

or

Comparator<String> c = Comparator.comparing((String x) -> x);

new MySortedLinkedList<String>(Comparator<String>);

When passing a parameter, you need to use an object instance, not an interface/class type. If you must use a comparator (if the MySortedLinkedList class has no support for using the natural ordering of Comparable objects), then you can make a "natural ordering" comparator:

private static class NaturalOrderingComparator<T extends Comparable<T>> implements Comparator<T>
{
   private static final Comparator<?> INSTANCE = new NaturalOrderingComparator<String>();
   private NaturalOrderingComparator(){} // singleton

   public static <U extends Comparable<U>> Comparator<U> getInstance()
   {
      @SuppressWarnings("unchecked")
      Comparator<U> comparator = (Comparator<U>) INSTANCE;
      return comparator;
   }
   
   public int compare(T a, T b)
   {
      return a.compareTo(b);
   }
}

And then use that:

MySortedLinkedList<String> t = new MySortedLinkedList<String>(NaturalOrderingComparator.getInstance());