/* StringSorterLenLexico.java
** An instance of this class has methods (inherited from its parent)
** by which to sort an array (or a segment thereof) into ascending order 
** using the classic Selection Sort algorithm.  What this class provides
** is a method that implements the "Length-Lexicographic" ordering relation
** upon Strings, which says that shorter strings precede longer strings and, 
** among strings of the same length, they are ordered lexicographically.
*/

public class StringSorterLenLexico extends Sorter<String> {

   /* Returns true iff s1 < s2 according to Length-Lexicographic
   ** ordering, which is to say that either
   ** (1) s1.length() < s2.length() or
   ** (2) s1.length() = s2.length and s1.compareTo(s2) < 0
   */
   protected boolean isLessThan(String s1, String s2)
   {
      final int lengthDiff = s1.length() - s2.length();
      if (lengthDiff != 0) { 
         return lengthDiff < 0;  // returns true if s1 is shorter than s2, 
      }                          // false if s1 is longer than s2
      else {
         return s1.compareTo(s2) < 0;   // s1 and s2 are of same length,
      }                                 // so revert to lexicographic order

}