Поясните как работают некоторые части кода

package com.misha.project;
 
public class ChangeProduct {
 
    public static Product getSelected(int item){
        for (Product p : Product.values()) {
            if (p.getNumber() == item) {
                return p;
            }
        }
        return null;
    }
}

package com.misha.project;
 
public class MenuProduct {
    public static void menu() {
        for (Product p : Product.values())
            System.out.println(p.getNumber() + ". " + "Product - " + p.getName() + " | Price - " + p.getPrice());
    }
}

package com.misha.project;
 
public enum Product {
    TWIX(1,40, "Twix"),
    SNICKERS(2,50, "Snickers"),
    WATER(3, 10, "Water"),
    JUICE(4, 60, "Juice");
 
    private int number;
    private int price;
    private String name;
 
    Product(int number, int price, String name) {
        this.number = number;
        this.price = price;
        this.name = name;
    }
 
    public int getNumber() {
        return number;
    }
 
    public int getPrice() {
        return this.price;
    }
 
    public String getName() {
        return this.name;
    }
}

package com.misha.project;
 
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import java.util.InputMismatchException;
import java.util.Scanner;
 
public class VendingMachine {
 
    private final static Logger logger = LogManager.getLogger(VendingMachine.class);
 
    public static void main(String[] args) {
 
        logger.info("Application launched");
 
        System.out.println("Vending machine");
        System.out.println("----------------");
        System.out.println("Product menu:");
 
        MenuProduct.menu();
 
        System.out.println("Choose a product");
 
        Scanner sc = new Scanner(System.in);
        try {
            int i = sc.nextInt();
            SelectionProduct.variableProduct(i);
            }
            catch (InputMismatchException e) {
                System.err.println("You didn't enter a number!");
                logger.error("The user entered a non-numeric value: " + e.getMessage());
        }
        finally {
            System.err.println("Completion of the program!");
        }
    }
}

package com.misha.project;
 
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import java.util.Scanner;
 
public class SelectionProduct {
 
    private final static Logger logger = LogManager.getLogger(SelectionProduct.class);
 
    public static void variableProduct(int i){
 
        Product prod = ChangeProduct.getSelected(i);
 
        try {
            if (prod != null) {
                System.out.println("Product selected: " + prod.getName() + " Price: " + prod.getPrice());
                System.out.println("Deposit money");
 
                Scanner sc = new Scanner(System.in);
 
                double cash = sc.nextInt();
 
                if (cash < prod.getPrice()) {
                    System.out.println("Not enough money");
                    System.out.println("Refund " + cash);
                    logger.warn("Not enough money has been deposited by the user. Refund: " + cash);
                }
                if (cash == prod.getPrice()) {
                    System.out.println("Pick up the product");
                }
                if (cash > prod.getPrice()) {
                    double out = cash - prod.getPrice();
                    System.out.println("Pick up the product " + "Change " + out);
                }
            } else {
                throw new AssertionError();
            }
        }
        catch (AssertionError e) {
            System.err.println("There is no selection for this product.!");
            logger.error("There is no selection for this product.: " + e.getMessage());
        }
    }
}