code: public StorableIndex<S> setDefaultDirection(Direction direction) {
          Direction[] directions = mDirections;
  
          unspecified: {
              for (int i=directions.length; --i>=0; ) {
                  if (directions[i] == Direction.UNSPECIFIED) {
                      break unspecified;
                  }
              }
              // Completely specified direction, so nothing to alter.
              return this;
          }
  
          directions = directions.clone();
          for (int i=directions.length; --i>=0; ) {
              if (directions[i] == Direction.UNSPECIFIED) {
                  directions[i] = direction;
              }
          }
  
          return new StorableIndex<S>(mProperties, directions, mUnique, mClustered, false);
      }
docs: Returns a StorableIndex instance with all unspecified directions set to
  the given direction. Returns this if all directions are already
  specified.
  
  @param direction direction to replace all unspecified directions