如何让我的方法在执行一次后重启我的方法？

Question

How can I alter my code to make it so that it reruns the if/else-if statements after being run once.

Eg How can I go: top menu>prompt for input(which is 2)>submenu>prompt for input(1 or2)>add/delete>back to top menu/subMenu

/**
 * A simple program of a grocery store, which assists
 * the purchases, calculate total price and display bill.
 **/

public class GroceryStore {

    // this method manages the entire shopping process
    public void start() {
        final String UPI = "wcor690";   // a constant for student UPI

        Stock stock = new Stock();
        stock.loadItems("stock.txt");
        Cart cart = new Cart();

        System.out.println("==============================================================");
        System.out.println("------This is a simple grocery store program by " + UPI + ".------");
        topMenu();
        int input = getChoice(1, 3);
        if (input == 1){
            stock.displayItems();
            topMenu();
        }
        else if (input == 2){
            subMenu();
            input = getChoice(1, 4);
            if (input == 1){
                String itemCode = Keyboard.readInput();
                cart.addItem(stock.findItem(itemCode));
                topMenu();
            }
            else if (input == 2){
                String itemCode = Keyboard.readInput();
                cart.deleteItem(itemCode);
                subMenu();
            }
            else if (input == 3){
                cart.checkOut();
            }
            else if (input == 4){
                cart.deleteAll();
                System.out.println("All items are cleared from the shopping cart");
                topMenu();
            }
        }
        else if (input == 3){
            System.out.println("Exit");
        }

        stock.saveItems("stock2.txt");
        System.out.println("--------------------------------------------------------------");
        System.out.println("---------------Thank you for shopping with us!----------------");
        System.out.println("=============================================================="); 
    }

    // this method displays the top-level menu
    private void topMenu() {
        System.out.println("1. Show items");
        System.out.println("2. Start shopping online");
        System.out.println("3. Exit");
    }

    // this method displays the second-level menu
    private void subMenu() {
        System.out.println("1. Add item");
        System.out.println("2. Remove item");
        System.out.println("3. Checkout");
        System.out.println("4. Exit without buying");
    }

    // this method gets the user's input choice
    private int getChoice(int lower, int upper) {
        String userInput = Keyboard.readInput();
        int input = Integer.parseInt(userInput);
        while (input<lower || input>upper){
            System.out.println("Invalid choice, please enter a valid choice");
            input = Integer.parseInt(Keyboard.readInput());
        }
        return input;
    }

}

Answer 1

You can use some sort of loop, which will continue to excecute the code until a condition is met.

Check out this link .

Here is an example:

do {
   code line 1;
   code line 2;
   code line 3;
   ...
} while(yourCondition);

If yourCondition is satisfied ( yourCondition == true ), the code will go back to code line 1 (will perform the code block between do and while ) and it'll stop once the condition isn't satisfied( yourCondition == false ).

Now, after you understand how it works, you can easily apply this to your code.