Shopping cart program in Java with a text menu I wrote this program to implement a shopping cart.  It supports adding/removing items to the cart, viewing the current order, and completing the checkout process.

import java.util.Scanner;

public class Keychains1 {

    public static Scanner keyboard = new Scanner(System.in);
    public static boolean stay = true;


    public static void add_keychains() {
        System.out.println("ADD KEYCHAINS");
    }

    public static void remove_keychains() {
        System.out.println("REMOVE KEYCHAINS");
    }

    public static void view_order() {
        System.out.println("VIEW ORDER");
    }

    public static void checkout() {
        System.out.println("CHECKOUT");
        stay = false;
    }


    public static void main(String[] args) {

        int choice;     

        while (stay) {

            System.out.println("Ye Olde Keychain Shoppe");
            System.out.println();

            System.out.println("1. Add Keychains to Order");
            System.out.println("2. Remove Keychains from Order");
            System.out.println("3. View Current Order");
            System.out.println("4. Checkout");
            System.out.println();
            System.out.print("Please enter your choice: ");

            choice = keyboard.nextInt();

            System.out.println();

            if (choice == 1) {
                add_keychains();
            }
            else if (choice == 2) {
                remove_keychains();
            }
            else if (choice == 3) {
                view_order();
            } 
            else if (choice == 4) {
                checkout();
            }
            else {
                System.out.println("Error. Please choose again.");
            }
            System.out.println();
        }

    }
}
Naming
I can't begin with another topic.
You use 2 different approaches to name your variables:

someName -&gt; it's a camelCase
some_name -&gt; it's a snake_case

Read this article to understand the difference
Java has own code style and you should use only camelCase for your variable name, class name, method name
I'll provide more examples about naming in Java.
Let's start with simple variable (not final, because final variable has own name convention)

someName - for variable (not final variable) name
someMethod - for method name
SomeClass - for class name

You may have final variable, it's commonly use in case when you need the property that will be general for all objects of the class and this property will not change.
private static int SOME_IMMUTABLE_VARIABLE = 10;

You need to fix names for your variables and methods:
remove_keychains -&gt; removeKeyChains() // in the same manner for others