///////    Sortable.java    ///////

/*
public interface name extends interface1, Interface2, ...
{  // all methods should be declared public (and abstract by dafault)
   // all vars should be declared public, static and final
}
*/

public interface Sortable
{/** compares elements i and j and 
  *   for element_i >, ==, < element_j returns
  *      > 0,  0, < 0  if direction is INCREASING
  *      < 0,  0, > 0  if direction is DECREASING
  */
      int compare(int i, int j); 

 /** swaps elements i and j */
      void swap(int i, int j);

 /** first element index */
      int first();  

 /** last element index */
      int last();   

 /** get/set sort flag */
      boolean sorted();
      void sorted(boolean b);

 /** get/set sort direction flag to INCREASING or DECREASING */
      void direction(int dir);
      int direction();

 /** possible direction flag values */
      static final int INCREASING = 1;
      static final int DECREASING = -1;
}