Simple Moving Average by each stock

SMAbyStock.java

import java.io.*;
import java.util.*;

/**
 * Created with IntelliJ IDEA.
 * User: joonhyunglim
 * Date: 5/25/13
 * Time: 6:34 PM
 * To change this template use File | Settings | File Templates.
 */
public class SMAbyStock {

        private final Queue<Double> window = new LinkedList<Double>(); // First in First Out
        private final int period;
        private double sum;

        public SMAbyStock(int period) {

            assert period > 0 : "Period must be a positive integer";
            this.period = period;

        }

        public void newNum(double num) {

            sum += num;
            window.add(num);

            if (window.size() > period) {

                sum -= window.remove();

            }

        }

        public double getAvg() {

            if (window.size() != period) return 0; // technically the average is undefined

            return sum / window.size();
        }

        public static void main(String[] args) throws IOException {

            long start = System.currentTimeMillis(); // this is for measuring the computation time.
            int[] windowSizes = {50,100,200};

            for (int windSize : windowSizes) { // it will create number of files based on your windowsize specification.


                // Writing the outcome for each window size.
                File outfile = new File("/Users/joonhyunglim/Desktop/MSiA/MSiA431/data/NASDAQ_Moving_Average_"+windSize+".csv");
                // you don't need to create the file previously, it will create the file if it does not exist
                if (outfile.createNewFile()) {
                    System.out.println("File created");
                } else {
                    System.out.println("I found the file. I am writing to the existing file");
                }
                BufferedWriter result = new BufferedWriter(new FileWriter(outfile));


                // Reading all files in the folder
                File folder = new File("/Users/joonhyunglim/Desktop/MSiA/MSiA431/data/NASDAQ/NASDAQ");
                File[] listOfFiles = folder.listFiles();

                for (File file : listOfFiles) {
                    BufferedReader Reader = new BufferedReader(new FileReader(file));

                    Reader.readLine(); // take out the column header

                    ArrayList<Double> Data = new ArrayList<Double>();
                    String line;
                    while ((line = Reader.readLine()) != null) {
                        String[] tokens = line.split(",");
                        Data.add(Double.parseDouble(tokens[6]));

                    }
                    System.out.println(Data.size());
                    Reader.close();


                    // Simple Moving Average
                    SMAbyStock ma = new SMAbyStock(windSize);


                    // sort the Hashtable by key and iterate them
                    for(Double x : Data) {
                        ma.newNum(x);
                        result.write(file.getName().split("\\.")[0]+","+x+"," + ma.getAvg()); // for each date, Left is a data point, and the right is a SMA.
                        result.newLine();
                    }


                }
                result.close();
            }
            long time = System.currentTimeMillis() - start;
            System.out.println("\n**Execution Time is : "+time/1000+"seconds**");
        }
}