public static Pair<String,String> checkSpecialSearch(String filter,char[] binarySortedPrefixes){
  if (filter.length() > 1 && Arrays.binarySearch(binarySortedPrefixes,filter.charAt(0)) >= 0) {
    return new Pair<>(filter.substring(0,1),filter.substring(1));
  }
  return null;
}

public static Pair < String , String > checkSpecialSearch ( String filter , char [ ] binarySortedPrefixes ) { if ( filter . length ( ) > 1 && Arrays . binarySearch ( binarySortedPrefixes , filter . charAt ( 0 ) ) >= 0 ) { return new Pair < > ( filter . substring ( 0 , 1 ) , filter . substring ( 1 ) ) ; } return null ; }
check if filter is a special search with prefix format : [ prefix ] . + e . g . # tag , ? phrase where # and ? are prefix characters
