Sinlge-thread program in multiple Java VM.

Question

I have a program that spawns two threads: one reads text line by line from a file, and places it in a LinkedBlockingQueue; The other takes stuff off the LinkedBlockingQueue, and processs it (no output to other file). Therefore this is a typical Producer and Consumer setup. I use two threads for one each. The program is run from Windows XP command window.
It runs fine. Processes big text files as expected, even though the CPU % is kind of high. Then, just for fun, I started five command windows to run one instance in each, but with different files. CPU % in task manager spikes to 100%, and the processing in each window slows down dramatically, to only about 2000 rows in every 30 or 40 seconds.
The code posted below is actul code of the program. Runs fine in single command window but terribly slow in multiple windows (with different data file.). The getAnswer() is a bad stuff. I should have had used Callable instead but it is not important.
Can anyone review the code and let me know what is the cause of slowdown, or I just should run it in mulitple instances in multiple command windows?
import java.io.*;
import java.util.*;
import java.util.concurrent.*;
// --------- file reading thread ----------------------
class fReader implements Runnable {
private LinkedBlockingQueue<ArrayList<String>> q=null;
private String input_f=null;
private BufferedReader br=null;
private int total=0;
public fReader(LinkedBlockingQueue<ArrayList<String>> q, String filename) throws IOException {
q=_q;
input_f=file_name;
br=new BufferedReader(new FileReader(input_f));
public int getAnswer(){return total;}
public void run(){
ArrayList<String> tb=new ArrayList<String>();
String s=null;
try {
while(true){
     for (int z=0; z<200; z++) {
          s=br.readLine();
          if (s==null) break;
          total++;
          tb.add(s.trim());
     if (s==null) break;
     q.put(tb);
     tb=new ArrayList<String>();
     Thread.yield();
tb.add(s);
q.put(tb);
br.close();
catch(IOException e1){}
catch(InterruptedException e2){}
// ----- file processing thread ----------
class fProc implements Runnable {
private LinkedBlockingQueue<ArrayList<String>> q=null;
private String output_f=null;
private PrintWriter pw=null;
private String match=null;
private int total=0;
public fProc(LinkedBlockingQueue<ArrayList<String>> q, String filename, String match_s) throws IOException {
output_f=file_name;
q=_q;
pw=new PrintWriter(new BufferedWriter(new FileWriter(output_f)));
match=match_s;
public int getAnswer(){return total;}
public void run(){
ArrayList<String> p=null;
boolean busy=true;
while(busy){
     p=q.poll();
     if (p==null) {
          Thread.yield();
          continue;
// loop, count, and print at the end of the processing
     Iterator ir=p.iterator();
     while(ir.hasNext()){
          String x=(String)ir.next();
          ir.remove();
          if (x==null){
               busy=false; break;
          else {
               String[] m=x.split("[,]");
               String[] n=m[2].split("[\"]"); // null(0), something(1), null(0)
               if (n[1].equals(match))
                    total++;
          Thread.yield();
     p=null;
     System.out.println("Processing");
if (pw!=null) pw.close();
// end of run()     
// end of class
public class pf2 {
private String date_value=null, fn_ext=null;
private File _file=null;
private File _dest=null;
public pf2(){_file=null;_dest=null;}
// -------------- application start point ----------------
public static void main(String[] args) throws IOException{
if (args.length!=1){
     System.out.println("Usage: java pf2 <filename.ext>");
     System.out.println("Example: java pf2 vwo.2011-01-18.csv");
     return;
String inputf=".\\original\\"+args[0];// args[0] is the filename with extension.
String outputf=".\\data\\"+args[0];// args[0] is the filename with extension.
// split the date string in input file name.
String[] date_s=args[0].split("[.]+")[1].split("[-]+");
String date2=String.format(
     "%s/%s/%s",
     Integer.toString(Integer.parseInt(date_s[1])),
     Integer.toString(Integer.parseInt(date_s[2])),
     Integer.toString(Integer.parseInt(date_s[0]))
ExecutorService es=Executors.newFixedThreadPool(4);
LinkedBlockingQueue<ArrayList<String>> q=new LinkedBlockingQueue<ArrayList<String>>();
fReader input=null;
fProc output=null;
try {
     input=new fReader(q, inputf);
     output=new fProc(q, outputf, date2);
catch(IOException e3){
     System.out.println(e3.getMessage());
     return;
// starts the program here
System.out.println("Running ....");
es.execute(input);
es.execute(output);
es.shutdown();
while(!es.isTerminated());
System.out.printf("Read %d row(s), %d of them are good.\n", input.getAnswer(), output.getAnswer());
float v=new Integer(output.getAnswer()).floatValue()/new Integer(input.getAnswer()).floatValue();
System.out.printf("Bad rate=%.2f%%.\n", (1-v)*100);
System.out.print("Press a key to continue.");
while(System.in.read()==-1);
// end of main()
// end of class pf
}

Answer 1

As @EJP suggests, disk work best when read serially. When the OS detects you are reading a file serially it will prefetch the next data you need. You may find that removing the reader thread is faster as you are doubling up what the OS does for you.
However, when you read multiple files from the same disk the head has to move around more, slowing it down significantly. I would suggest only using multiple readers when you have multiple independent disks. (Though I have never seen this work well on Windows, only on Unix)