String readSubstring(String source,int ofs,int end){
  if (source == null || ofs > source.length() || end > source.length()) {
    return null;
  }
  return source.substring(ofs,end);
}

String readSubstring ( String source , int ofs , int end ) { if ( source == null || ofs > source . length ( ) || end > source . length ( ) ) { return null ; } return source . substring ( ofs , end ) ; }
read an substring from source .
