Switch/Case Java return to main menu

Im writing a program for my Java class and i need to make a receipt like output. I have to allow the user to choose from 3 items. After choosing the item, they choose the quantity, and i multiply that by the price to give them a total. The user needs to pick all 3 items, but can pick them in any order. I am trying to make a Switch/Case method to help me assign the variables to what the user has chosen. This is what i have currently:

System.out.println("Enter name of First item");
    System.out.println(" 1. Gum, 2. Soda, 3. Chips");
    firstItem = keyboard.nextInt( );
    switch (firstItem)
{
case 1:
   System.out.println("Gum");
   System.out.println(gumPrice);
   System.out.println("How many packs of gum would you like to purchase?");
   gumBought = keyboard.nextInt();

   break;
   case 2:
   System.out.println("Soda");
   System.out.println(sodaPrice);
   System.out.println("How many cups of soda would you like to purchase?");
   sodaBought = keyboard.nextInt();
    break;
case 3:
   System.out.println("Chips");
   System.out.println(chipsPrice);
   System.out.println("How many bags of chips would you like to purchase?");
   chipsBought = keyboard.nextInt();
   break;
default:
   System.out.println("Unknown Entry");
   break;

}

And Then it begins the second item Switch/Case. I Need to know how to get it to return to the Main Question (Gum/Soda/Chips) if the user picks a number outside of 1-3 or picks the same number/item twice. How can i do this efficiently?

Also, can i use Strings instead of Int to allow the user to type "Gum" instead of "1"? Thanks.