How to write to the end of a file

Question

i am tryign to write to the end of a file using bufferwriter and bufferreadear. I am trying to the read the file until i reach the end and then write in the end. I have some code but i dont know how to read until the end of the file.
File file = new  File ("Product.txt");
          FileReader reader = new FileReader (file);
          BufferedReader readBuff = new BufferedReader (reader);
          FileWriter write = new FileWriter(file);
          BufferedWriter writeBuff = new BufferedWriter(write);
          String line = readBuff.readLine();     
// i know i need to put a while loop somewhere around here

Answer 1

I want to write to the end of the file, what do you mean when you say "then write() until you've written that many bytes, which will overwrite the bytes already in the file."
          File file = new  File ("Products.txt");
          FileReader reader = new FileReader (file);
          BufferedReader readBuff = new BufferedReader (reader);
          FileWriter write = new FileWriter(file);
          BufferedWriter writeBuff = new BufferedWriter(write);
          String line = readBuff.readLine();
          long fileSize = file.length();
          readBuff.close();
          writeBuff.close();
          } catch (IOException e){
               System.out.println ("Error -- " + e.toString());
     }