How to Read from two file and write to another file --Please help !!

Question

Hi all,
Please suggest me where i'm goin goin wrng.
I have 2 flat files. one of them is the main file(Ann.dat) has a about 150,000 lines (each line has unique ID from 00001 to 45000) of data and the the other(Miss.dat) has a just a list of IDs that are no longer in use & have to be deleted from the first file(NewAnn.dat). (Note that Ann.dat is a tab delimitted file and Miss.dat is just a list of all invalid IDs)
Below is my code. It doesn't do what I'm supposed to. Please suggest me or help me with a code to do it. What I'm trying to do is read each of the lines from the 2 files compare the ID in ann.dat with all the IDs in Miss.dat & if it doesn't match with the ID in Miss.dat write the whole line to NewAnn.dat. And do the rest with all the lines in Ann.dat.
It could be a real dumb question. since i'm not a software professional, I consider myself to be newbie to programming. I desperately need your help.
import java.io.*;
import java.util.*;
public class anntemp{
     public static void main(String[] args)
          String keyAnn ="";
          String keyMis="";
          String recAnn =null;
          String recMis =null;
          try{               
          FileReader fr=new FileReader("C:\\Tom\\Ann.dat");
          BufferedReader br=new BufferedReader(fr);
          int couter=0;
          while ((recAnn = br.readLine())!=null)
               couter++;
               keyAnn = recAnn.substring(0, recAnn.indexOf("\t"));
          FileReader fr1=new FileReader("C:\\Tom\\Miss.dat");
          BufferedReader br1=new BufferedReader(fr1);
          while((recMis = br1.readLine())!=null){
          keyMis = recMis.substring(0, recMis.indexOf("\t"));
               if(keyAnn.equals(keyMis)){
     FileWriter fw=new FileWriter("C:\\Tom\\NewAnn.dat",true);
     BufferedWriter bw=new BufferedWriter(fw);
     PrintWriter pw=new PrintWriter(bw);
     StringBuffer writeValue = new StringBuffer();
     writeValue.append(recAnn);
                                             pw.println(writeValue.toString());
     pw.flush();
          }catch (Exception expe){
               System.out.println("In Exception ");
               expe.printStackTrace();
Thank you all in advance,
br

Answer 1

I think you need to close the files when you are done in the inner loop. Plus I think you'll be overwritting the file in the inner loop if more than one match. It might be easier to read the unused id file into a map at the start, and then loop up the id's from the master file in the map. You can put the unused id's in as the keys, and a Boolean.TRUE as the value (value won't matter). Then just check if the map contains the key for the id read from the master file. That should cut down on disk activity. This assumes the unused id file is smallish.