NumberFormatException for Input String Java

I am writing an appointment program in Java and am coming across an error which is

Exception in thread "main" java.lang.NumberFormatException: For input string : ""

for the following lines :

at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
at java.lang.Integer.parseInt(Integer.java:470)
at java.lang.Integer.parseInt(Integer.java:499)
at AppointmentNew.main(AppointmentNew.java:24)

The program is going through once, but once it gets to the end of its first run it gives me those errors.... For instance when I run the program as follows : I make the choice of "1" to make a new appointment, I then enter the date of my new appointment "mm/dd/yyyy", then I add an appointment description, and lastly I enter the type "Once, Daily, or Monthly". After that finishes it should start back over with the very first line of "Make Choice (1: New, 2: Print Range, 3: Print All, quit):" But instead it gives me the errors I described above...

Here is my code I have.

import java.util.*;

public class AppointmentNew 
{
public static void main (String[] args)
{
  ArrayList<String> list = new ArrayList<String>();
  Scanner stdin = new Scanner(System.in);
  String choice = "";
  int choiceNum = 0;
  String date = "";
  String descrip = "";
  int type = 0;
  String typeChose = "";

  System.out.println("Welcome to Appointment App!\n");
  System.out.println("\t============================\n");

  do
  {
     System.out.print("\tMake Choice ( 1: New, 2: Print Range, 3: Print All, quit): ");
     choice = stdin.nextLine();

     choiceNum = Integer.parseInt(choice);

     if (choiceNum == 1)
     {
        System.out.print("\n\n\tEnter New Appointment Date in mm/dd/yyyy format: ");
        date = stdin.nextLine();

        System.out.print("\n\n\tEnter New Appointment Description: ");
        descrip = stdin.nextLine();

        System.out.print("\n\n\tEnter Type (1 = Once, 2 = Daily, 3 = Monthly): ");
        type = stdin.nextInt();
        if (type == 1)
        {
          Once once = new Once(date, descrip);
           typeChose = "One-Time";
        }
        else if (type == 2)
        {
          Daily daily = new Daily(date, descrip);
           typeChose = "Daily";
        }
        else
        {
          Monthly monthly = new Monthly(date, descrip);
           typeChose = "Monthly";
        }
          String stringToAdd = "";
          stringToAdd = ("\n\n\tNew " + typeChose + " Appointment Added for " + date + "\n");
          list.add(stringToAdd);

        System.out.println(stringToAdd);
        System.out.println("\t============================\n");

     }

     if (choiceNum == 2)
     {
     System.out.print("\n\n\tEnter START Date in mm/dd/yyyy format: ");
     String lowDate = stdin.nextLine();
     System.out.print("\n\n\tEnter END Date in mm/dd/yyyy format: ");
     String highDate = stdin.nextLine();

     for(int i = 0; i < list.size(); i++)
        {
         int dateSpot = list.get(i).indexOf(" ");
         if (list.get(i).compareTo(lowDate) <= 0 && list.get(i).compareTo(highDate) >= 0)
        {
           System.out.println(list.get(i));   
       }}
     }

     if (choiceNum == 3)
     {
       for(int i = 0; i < list.size(); i++)
       {
          System.out.println(list.get(i));     
       }
     }

  }while (choice != "quit");      
}
}

Any help would be great!