public static void main(String[] args) {

    // create a ProductMatcher object to match the listings to product. The constructor take a
    // string as the name of output file
    ProductMatcher pMatcher = new ProductMatcher("data/output.txt");
    if (args.length < 2) {
      System.out.println("Proper Usage is: java Main productsInput listingsIuput");
      System.exit(0);
    }

    // parse the json strings from the input file use ProductMatcher pMatcher.
    parseInput(args[0], pMatcher, 0);
    parseInput(args[1], pMatcher, 1);

    // match listing objects to product objects
    pMatcher.match();

    // print the result to output.txt
    pMatcher.printResult();
  }