classes

restaurant/Address.java

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+public class Address {
+    private double longitude;
+    private double latitude;
+    private String writtenAddress;
+
+    public Address(double latitude, double longitude, String writtenAddress){
+        this.latitude = latitude;
+        this.longitude = longitude;
+        this.writtenAddress = writtenAddress;
+    }
+
+    public double getLatitude() {
+        return latitude;
+    }
+
+    public double getLongitude() {
+        return longitude;
+    }
+
+    public String getWrittenAddress() {
+        return writtenAddress;
+    }
+
+    public double distanceFrom(Address target) {
+        return Math.sqrt(
+            Math.pow((this.latitude - target.getLatitude()), 2)
+            +
+            Math.pow((this.longitude - target.getLongitude()), 2)
+        );
+    }
+}

restaurant/Customer.java

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+public class Customer {
+    private int number;
+    private String name;
+    private Address address;
+
+    public Customer(int number, String name, Address address) {
+        this.number = number;
+        this.name = name;
+        this.address = address;
+    }
+
+    public int getCustomerNumber() {
+        return number;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public Address getAddress() {
+        return address;
+    }
+
+    public void setAddress(Address address) {
+        this.address = address;
+    }
+}

restaurant/Food.java

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+import java.util.Vector;
+
+public class Food {
+    private String name;
+    private int price;
+
+    private static Vector<Food> menu = new Vector<Food>();
+
+    public Food(String name, int price) {
+        this.name = name;
+        this.price = price;
+
+        menu.add(this);
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public int getPrice() {
+        return price;
+    }
+
+    public static Vector<Food> getMenu() {
+        return menu;
+    }
+}

restaurant/Invoice.java

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+import java.util.Vector;
+
+class Invoice {
+    private static final float taxRate = 9.4;
+    private Customer customer;
+    private boolean acceptingOrder;
+    private Vector<Item> items;
+
+    public Invoice(Customer customer) {
+        this.customer = customer;
+        this.acceptingOrder = true;
+        this.items = new Vector<Item>();
+    }
+
+    public boolean addItem(Item item) {
+        if (acceptingOrder) {
+            items.add(item);
+        }
+        return acceptingOrder;
+    }
+
+    public boolean removeItem(Item item) {
+        if (acceptingOrder) {
+            return items.remove(item);
+        }
+        return false;
+    }
+
+    public void nextStage() {
+        this.acceptingOrder = false
+    }
+
+    public int getState() {
+        return state;
+    }
+
+    public int getTotalPrice() {
+        double total = 0;
+        for (Item item : items) {
+            total += item.getFood().getPrice() * item.getCount();
+        }
+        return (int) (total * (taxRate + 100) / 100);
+    }
+
+    public Customer getCustomer() {
+        return customer;
+    }
+
+    public Vector<Item> getItems() {
+        return items;
+    }
+}

restaurant/Item.java

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+public class Item {
+    private Food food;
+    private int count;
+    private String description;
+
+    public Item(Food food, int count, String description) {
+        this.food = food;
+        this.count = count;
+        this.description = description;
+    }
+
+    public Item(Food food, int count) {
+        this.food = food;
+        this.count = count;
+        this.description = "";
+    }
+
+    public Food getFood() {
+        return food;
+    }
+
+    public int getCount() {
+        return count;
+    }
+
+    public String getDescription() {
+        return description;
+    }
+}

restaurant/Main.java

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+public static void Main(String[] args) {
+    Address a1 = new Address(2, 3, "Lahijan");
+    Address a2 = new Address(5, 6, "Tehran");
+
+    System.out.println("\n--------------------------------------\n");
+    System.out.println("Distance From Address a1 to a2 is: " + a1.distanceFrom(a2));
+    System.out.println("\n--------------------------------------\n");
+
+    Customer c1 = new Customer("MAMAD", a1);
+    Customer c2 = new Customer("ALI", a2);
+
+    System.out.println("First Customer's ID: " + c1.getCustomerNumber());
+    System.out.println("Second Customer's ID: " + c2.getCustomerNumber());
+
+    Food f1 = new Food("BURGER", 130);
+    Food f2 = new Food("PIZZA", 200);
+    Food f3 = new Food("PASTA", 110);
+
+    System.out.println("\n--------------------------------------\n");
+
+    for (int i = 0; i < Food.getMenu().size(); i++) {
+        System.out.println("Food Name: " + Food.getMenu().get(i).getName());
+    }
+
+    System.out.println("\n--------------------------------------\n");
+
+    Item it1 = new Item(f1, 2);
+    Item it2 = new Item(f2, 3, "MORE SAUCE");
+    Item it3 = new Item(f3, 1);
+
+    Invoice inv = new Invoice(c1);
+
+    if (inv.addItem(it1) && inv.addItem(it2)) System.out.println("Items added successfully");
+    else System.out.println("Items could not be added");
+
+    if (inv.removeItem(it3)) System.out.println("Item removed successfully");
+    else System.out.println("Failed to remove item (item doesn't exist in invoice)");
+
+    inv.nextStage();
+
+    System.out.println("Current state: " + inv.getState());
+
+    System.out.println("\n--------------------------------------\n");
+
+    for (int i = 0; i < inv.getItems().size(); i++) {
+        Item it = inv.getItems().get(i);
+        System.out.println("Food Name: " + it.getFood().getName() + " | Food Description: " + it.getDescription());
+    }
+
+    System.out.println("Total price: " + inv.getTotalPrice());
+}