CSV file combiner — this simple program takes all textfiles in a folder and add all the text files into one giant textfile.

CSVcombiner.java

import java.io.*;

/**
 * Created with IntelliJ IDEA.
 * User: joonhyunglim
 * Date: 5/25/13
 * Time: 5:42 PM
 * To change this template use File | Settings | File Templates.
 */
public class CSVcombiner {

    // this program is written to combine same format text files into one giant file
    public static void main(String[] args) throws IOException {

        long start = System.currentTimeMillis(); // this is for measuring the computation time.
        double rand;


        // write out the analyzed file to this address below
        File fileout = new File("/Users/joonhyunglim/Desktop/MSiA/MSiA431/DATA/NASDAQ_daily_combined.csv");

        // you don't need to create the file previously, it will create the file if it does not exist
        if (fileout.createNewFile()) {
            System.out.println("File created");
        } else {
            System.out.println("I found the file. I am writing to the existing file");
        }
        BufferedWriter output = new BufferedWriter(new FileWriter(fileout));

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

        for (File file : listOfFiles) {
            if (file.isFile()) {

                int rownum = 0;
                System.out.println("\nWorking file is: "+file);

                BufferedReader input = new BufferedReader(new FileReader(file));

                input.readLine(); // take the header out.

                // this bracket below is the part for actual analysis.
                try {
                    String line;
                    while ((line = input.readLine()) != null) {

                        output.write(line);
                        output.newLine();
                        rownum++;

                    }
                    input.close();
                    System.out.println(file +" has been written." + " Size is: "+rownum);


                } catch(IOException e) {
                    e.printStackTrace();
                } catch(IllegalArgumentException ae) {
                    ae.printStackTrace();
                }

            } else {
                System.out.println("Error: No file was found in this directory.");
            }

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