code: public SortDirection nextDirection(SortDirection direction) {
          if(direction == SortDirection.NONE)
              return SortDirection.ASCENDING;
          else if(direction == SortDirection.ASCENDING)
              return SortDirection.DESCENDING;
          else if(direction == SortDirection.DESCENDING)
              return SortDirection.NONE;
          else throw new IllegalStateException(Bundle.getErrorString("SortStrategy_InvalidSortDirection", new Object[]{direction}));
      }
docs: <p>
  Given a sort direction, get the next sort direction.  This implements a simple sort machine
  that cycles through the sort directions in the following order:
  <pre>
  SortDirection.NONE > SortDirection.ASCENDING > SortDirection.DESCENDING > repeat
  </pre>
  </p>
  @param direction the current {@link SortDirection}
  @return the next {@link SortDirection}