reading & parsing problem with rdf file which is approximately 1GB

Hello I am in trouble when I try to read geowordnet.rdf file with java when I use
InputStream in = FileManager.get().open(inputFileName);
but I can read it when I use following codes ;
f = new File ("geowordnetX.rdf");
long length = f.length();
long readedBytes = 0;
System.out.println(length);
try {
BufferedReader fr = new BufferedReader(new FileReader(f));
line = "";
while((fr.readLine().toString()) != null){
readedBytes += line.getBytes().length;
if(readedBytes > length){
break;
}else{
line += fr.readLine().toString() ;
System.out.println(line);
}
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}

But the problem is I can easily able to parse the rdf when file when I use first way Inputstream, Of course
I dont use whole file, instead I copy some info of rdf to another file and I can read it. Inputstream does not read
geowordnet because file size 700 Mb.
I can read whole file with second buffered way but this time it gives error when I try to parse it. The error is like that ;
Content is not allowed in prolog.
Exception in thread "main" com.hp.hpl.jena.shared.JenaException: org.xml.sax.SAXParseException: Content is not allowed in prolog.
at com.hp.hpl.jena.rdf.model.impl.RDFDefaultErrorHand ler.fatalError(RDFDefaultErrorHandler.java:45)
at com.hp.hpl.jena.rdf.arp.impl.ARPSaxErrorHandler.fa talError(ARPSaxErrorHandler.java:35)
at com.hp.hpl.jena.rdf.arp.impl.XMLHandler.warning(XM LHandler.java:225)

I do not know how to solve ? do you have any idea please ?
thanks