@VisibleForTesting int exactBinarySearch(long searchX,int startSearchIndex){
  return approximateBinarySearch(searchX,startSearchIndex,mData.size() - 1,true,0);
}

@ VisibleForTesting int exactBinarySearch ( long searchX , int startSearchIndex ) { return approximateBinarySearch ( searchX , startSearchIndex , mData . size ( ) - 1 , true , 0 ) ; }
searches for the index of the value that is equal to or just less than the search x value , in the range of startsearchindex to the end of the data array .
