adding files

first/Address.java

@@ -0,0 +1,48 @@
+public class Address{
+    public double latitude;
+    public double longitude;
+    public String written_address;
+
+    public Address(double latitude, double longitude, String written_address) {
+        this.latitude = latitude;
+        this.longitude = longitude;
+        this.written_address = written_address;
+    }
+
+      public double distanceFrom(Address otherAddress) {
+        double la1 = this.latitude;
+        double lo1 = this.longitude;
+        double la2 = otherAddress.latitude;
+        double lo2 = otherAddress.longitude;
+        double longitude=lo2 - lo1;
+        double latitude = la2-la1;
+        double power1=Math.pow(longitude,2);
+        double power2=Math.pow(latitude , 2);
+        double Distance= Math.sqrt(power1+power2);
+        double distanceRound=Math.round(Distance * 100000)/100000.0;
+        return distanceRound;
+    }
+    public double getLatitude(){
+        return latitude;
+    }
+    public void setLatitude(double newlatitude){
+        this.latitude=newlatitude;
+    }
+    public double getLongitude(){
+        return longitude;
+    }
+    public void setLongitude(double newlongitude){
+        this.longitude=newlongitude;
+    }
+     public String getWrittenAddress() {
+        return written_address;
+    }
+
+    public void setWrittenAddress(String newwritten_address) {
+        this.written_address = newwritten_address;
+    }
+
+
+}
+
+

first/Customer.java

@@ -0,0 +1,27 @@
+public class Customer{
+    private static int nextCustomerNumber = 1;
+    private  final int customerNumber;
+    private String name;
+    private Address address;
+
+    public Customer(String name , Address address){
+        this.customerNumber= nextCustomerNumber++;
+        this.name=name;
+        this.address = address;
+    }
+    public int getCustomerNumber(){
+        return customerNumber;
+    }
+    public String getName(){
+        return name;
+    }
+    public Address getAddress(){
+        return address;
+    }
+    public void setName(String name){
+        this.name = name;
+    }
+    public void setAddress(Address address){
+        this.address = address;
+    }
+}

first/Food.java

@@ -0,0 +1,23 @@
+import java.util.Vector;
+public class Food{
+    private final String name;
+    private final int price;
+    private static Vector<Food> menu= new Vector<>();
+
+    public Food(String n , int p){
+        this.name=n;
+        this.price = p;
+        menu.add(this);
+
+    }
+    public static Vector<Food> getMenu(){
+        return menu;
+    }
+    public int getPrice(){
+        return price;
+    }
+    public String getName(){
+        return name;
+    }
+
+}

first/Invoice.java

@@ -0,0 +1,52 @@
+import java.util.ArrayList;
+import java.util.List;
+public class Invoice{
+    private int state;
+    private Customer customer;
+    private List<Item> items;
+    private static final double tax_rate = 0.094;
+
+    public Invoice(Customer customer){
+        this.customer = customer;
+        this.state = -1;
+        this.items=new ArrayList<>();
+    }
+     public int getState(){
+            return this.state;
+        }
+        public Customer getCustomer(){
+            return this.customer;
+        }
+    public boolean addItem(Item item){
+        if (this.state == -1){
+            items.add(item);
+            return true;
+        }
+        else{
+            return false;}
+    }
+    public boolean removeItem(Item item){
+        if (this.state== -1 && items.contains(item)){
+            items.remove(item);
+            return true;
+        }
+        else{
+            return false;}
+        }
+        public void nextStage(){
+            this.state= state+1;
+        }
+        public int getTotalPrice(){
+            double total =0 ; 
+            for(Item item : items){
+                total += item.getFood().getPrice() * item.getCount();
+            }
+            total += total * tax_rate;
+            return (int) Math.ceil(total);
+        }
+        public List<Item> getItems(){
+            return items;
+        } 
+
+    }
+

first/Item.java

@@ -0,0 +1,27 @@
+public class Item{
+    private final Food food;
+    private final int count;
+    private final String description;
+
+    public Item(Food food , int count){
+        this.count=count;
+        this.food=food;
+        this.description="-";
+    }
+
+    public Item(Food food , int count , String d){
+        this.count=count;
+        this.food=food;
+        this.description=d;
+    }
+    public int getCount(){
+        return count;
+    }
+    public Food getFood(){
+        return food;
+    }
+    public String getDescription(){
+        return description;
+    }
+
+}

first/Restaurant.java

@@ -0,0 +1,53 @@
+public class Restaurant{
+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());
+}
+}