Reading a 2GB file and writing to two differnt files based on a delimiter

Question

Good Morning!
I have to to read the content of 2 gb file(main.txt) and copy its content into two other files based on a delimiter.The delimiter is '/'. Initially i have to start writing the contents of main.txt to copy1.txt as soon as i encounter a delimiter i have to write the contents to copy2.txt again if i encounter next delimiter i have to write the contents copy1.txt and so on
This is my piece of code but it takes 20-25 minutes.How can i optimise this operation.efficiency is my problem
try{
     FileInputStream fis = new FileInputStream ("main.txt");
     FileOutputStream foscopy1 = new FileOutputStream ("copy1.txt") ;
     FileOutputStream foscopy2 = new FileOutputStream ("copy2.txt") ;
     int iFlag=1;
     int s;
     while((s=fis.read())!=-1)
          System.out.println(iFlag);
          if (s=='/')
               iFlag=-iFlag ;
          else{
     if (iFlag==1)
                    foscopy1.write(s);
else
foscopy2.write(s);
if u canprovide code that would do a lot of good

Answer 1

Perhaps you could use a StreamTokenizer on top of a BufferedReader since you are using text files... The buffered reader will buffer your input so that it doesn't have to perform IO on every byte read. Subsequently the output may also be buffered to enhance performance...
StreamTokenizer st = new StreamTokenizer(new BufferedReader(new FileReader("main.txt")));
st.whitespaceChars('/', '/');
BufferedWriter out = new BufferedWriter(new FileWriter("copy1.txt"));
//same with copy 2
while (st.nextToken() != st.TT_EOF) { // while not end
  String s = st.sval;
  // determiine copy to write to, then write.
}