public static void main(String args[])
      throws DbException, TransactionAbortedException, IOException {
    // convert a file
    if (args[0].equals("convert")) {
      try {
        if (args.length == 3) {
          HeapFileEncoder.convert(
              new File(args[1]),
              new File(args[1].replaceAll(".txt", ".dat")),
              BufferPool.PAGE_SIZE,
              Integer.parseInt(args[2]));
        } else if (args.length == 4) {
          ArrayList<Type> ts = new ArrayList<Type>();
          String[] typeStringAr = args[3].split(",");
          for (String s : typeStringAr) {
            if (s.toLowerCase().equals("int")) ts.add(Type.INT_TYPE);
            else if (s.toLowerCase().equals("string")) ts.add(Type.STRING_TYPE);
            else {
              System.out.println("Unknown type " + s);
              return;
            }
          }
          HeapFileEncoder.convert(
              new File(args[1]),
              new File(args[1].replaceAll(".txt", ".dat")),
              BufferPool.PAGE_SIZE,
              Integer.parseInt(args[2]),
              ts.toArray(new Type[0]));

        } else {
          System.out.println("Unexpected number of arguments to convert ");
        }
      } catch (IOException e) {
        throw new RuntimeException(e);
      }
    } else if (args[0].equals("print")) {
      File tableFile = new File(args[1]);
      int columns = Integer.parseInt(args[2]);
      DbFile table = Utility.openHeapFile(columns, tableFile);
      TransactionId tid = new TransactionId();
      DbFileIterator it = table.iterator(tid);

      if (null == it) {
        System.out.println(
            "Error: method HeapFile.iterator(TransactionId tid) not yet implemented!");
      } else {
        it.open();
        while (it.hasNext()) {
          Tuple t = it.next();
          System.out.println(t);
        }
        it.close();
      }
    } else if (args[0].equals("parser")) {
      // Strip the first argument and call the parser
      String[] newargs = new String[args.length - 1];
      for (int i = 1; i < args.length; ++i) {
        newargs[i - 1] = args[i];
      }

      try {
        // dynamically load Parser -- if it doesn't exist, print error message
        Class<?> c = Class.forName("simpledb.Parser");
        Class<?> s = String[].class;

        java.lang.reflect.Method m = c.getMethod("main", s);
        m.invoke(null, (java.lang.Object) newargs);
      } catch (ClassNotFoundException cne) {
        System.out.println(
            "Class Parser not found -- perhaps you are trying to run the parser as a part of lab1?");
      } catch (Exception e) {
        System.out.println("Error in parser.");
        e.printStackTrace();
      }

    } else {
      System.err.println("Unknown command: " + args[0]);
      System.exit(1);
    }
  }