Design a Logistics System

Difficulty Level : Medium
Last Updated : 13 Oct, 2018

Design a Logistics System (Object Oriented Design). Tell about the different classes and their relationships with each-other. It is not a System Design question, so scope of this question is only to define different classes (with it’s attributes and methods)

Asked In: Adobe

Solution: Let’s assume we want to design a Logistics System with following basic functionality:

• The system can take an order to deliver it to a given destination.
• The order will be a list of items and there is a cost of each order to process.
• User has to register himself / herself to use this system.
• User can track his / her order.
• Orders will be shipped by bike or truck, but only a single order will be shipped by a single vehicle.

These type of questions are asked in interviews to Judge the Object Oriented Design skill of a candidate. So, first of all we should think about the classes.

The main classes will be:

1. User
2. Item
3. Vehicle
4. Location
5. PaymentDetails
6. Order
7. LogisticsSystem

The User class is for users/clients/customers, who will be charged to get their items delivered.

public class User { 
  
    private int userId; 
    private String name; 
    private Location adress; 
    private String mobNo; 
    private String emailId; 
  
    public int getUserId() 
    { 
        return userId; 
    } 
  
    public void setUserId(int userId) 
    { 
        this.userId = userId; 
    } 
  
    public String getName() 
    { 
        return name; 
    } 
  
    public void setName(String name) 
    { 
        this.name = name; 
    } 
  
    public Location getAdress() 
    { 
        return adress; 
    } 
  
    public void setAdress(Location adress) 
    { 
        this.adress = adress; 
    } 
  
    public String getMobNo() 
    { 
        return mobNo; 
    } 
  
    public void setMobNo(String mobNo) 
    { 
        this.mobNo = mobNo; 
    } 
  
    public String getEmailId() 
    { 
        return emailId; 
    } 
  
    public void setEmailId(String emailId) 
    { 
        this.emailId = emailId; 
    } 
} 

Item class represents an item which will be shipped. An order will contain a list of items.

public class Item { 
  
    private String name; 
    private int price; 
    private int volume; 
    private int weight; 
  
    public String getName() 
    { 
        return name; 
    } 
  
    public void setName(String name) 
    { 
        this.name = name; 
    } 
  
    public int getPrice() 
    { 
        return price; 
    } 
  
    public void setPrice(int price) 
    { 
        this.price = price; 
    } 
  
    public int getVolume() 
    { 
        return volume; 
    } 
  
    public void setVolume(int volume) 
    { 
        this.volume = volume; 
    } 
  
    public int getWeight() 
    { 
        return weight; 
    } 
  
    public void setWeight(int weight) 
    { 
        this.weight = weight; 
    } 
} 

Location class simply represents the address.

public class Location { 
  
    private Double longitude; 
    private Double latitude; 
  
    public Double getLongitude() 
    { 
        return longitude; 
    } 
  
    public void setLongitude(Double longitude) 
    { 
        this.longitude = longitude; 
    } 
  
    public Double getLatitude() 
    { 
        return latitude; 
    } 
  
    public void setLatitude(Double latitude) 
    { 
        this.latitude = latitude; 
    } 
} 

The Vehicle class represents the vehicle which will be used to ship/deliver an order.
It will be of two types: 1. Bike and 2. Truck

public class Vehicle { 
  
    private int id; 
    private String vehicleNo; 
    private int capacity; 
    private Location currentPosition; 
    private VehicleStatus currentStatus; 
  
    public Vehicle(int id, String vehicleNo, int capacity) 
    { 
        this.id = id; 
        this.vehicleNo = vehicleNo; 
        this.capacity = capacity; 
    } 
  
    public int getId() 
    { 
        return id; 
    } 
  
    public void setId(int id) 
    { 
        this.id = id; 
    } 
  
    public String getVehicleNo() 
    { 
        return vehicleNo; 
    } 
  
    public void setVehicleNo(String vehicleNo) 
    { 
        this.vehicleNo = vehicleNo; 
    } 
  
    public int getCapacity() 
    { 
        return capacity; 
    } 
  
    public void setCapacity(int capacity) 
    { 
        this.capacity = capacity; 
    } 
  
    public Location getCurrentPosition() 
    { 
        return currentPosition; 
    } 
  
    public void setCurrentPosition(Location currentPosition) 
    { 
        this.currentPosition = currentPosition; 
    } 
  
    public VehicleStatus getCurrentStatus() 
    { 
        return currentStatus; 
    } 
  
    public void setCurrentStatus(VehicleStatus currentStatus) 
    { 
        this.currentStatus = currentStatus; 
    } 
} 

The bike has only 10 unit of capacity.

public class Bike extends Vehicle { 
  
    private final static int capacityofBike = 10; 
  
    public Bike(int id, String vehicleNo) 
    { 
  
        super(id, vehicleNo, capacityofBike); 
    } 
} 

The truck has only 100 unit of capacity (10 times more than bike).

public class Truck extends Vehicle { 
  
    private final static int capacityofTruck = 100; 
  
    public Truck(int id, String vehicleNo) 
    { 
        super(id, vehicleNo, capacityofTruck); 
    } 
} 

Enum for current status of a vehicle:

public enum VehicleStatus { 
    FREE, 
    BUSY, 
    NOT_WORKING; 
} 

Enum for OrderPriority:

public enum OrderPriority { 
    LOW, 
    MEDIUM, 
    HIGH; 
} 

Enum for OrderStatus:

public enum OrderStatus { 
    DELIVERED, 
    PROCESSING, 
    CANCELLED; 
} 

Enum for PaymentMode:

public enum PaymentMode { 
  
    NET_BANKING, 
    CREDIT_CARD, 
    DEBIT_CARD; 
} 

Enum for PaymentStatus:

public enum PaymentStatus { 
    PAID, 
    UNPAID; 
} 

The PaymentDetails class contains the information of payment related things so that in any case the order is cancelled, it can be refunded easily.

public class PaymentDetails { 
    private PaymentMode paymentMode; 
    private String transactionId; 
    private int amount; 
    private PaymentStatus paymentStatus; 
    private String cardNumber; 
  
    public PaymentMode getPaymentMode() 
    { 
        return paymentMode; 
    } 
  
    public void setPaymentMode(PaymentMode paymentMode) 
    { 
        this.paymentMode = paymentMode; 
    } 
  
    public String getTransactionId() 
    { 
        return transactionId; 
    } 
  
    public void setTransactionId(String transactionId) 
    { 
        this.transactionId = transactionId; 
    } 
  
    public int getAmount() 
    { 
        return amount; 
    } 
  
    public void setAmount(int amount) 
    { 
        this.amount = amount; 
    } 
  
    public PaymentStatus getPaymentStatus() 
    { 
        return paymentStatus; 
    } 
  
    public void setPaymentStatus(PaymentStatus paymentStatus) 
    { 
        this.paymentStatus = paymentStatus; 
    } 
  
    public String getCardNumber() 
    { 
        return cardNumber; 
    } 
  
    public void setCardNumber(String cardNumber) 
    { 
        this.cardNumber = cardNumber; 
    } 
} 

The Order class contains all the information of an order. All fields are self-explanatory.

import java.util.Date; 
import java.util.List; 
  
public class Order { 
  
    private int orderId; 
    private OrderPriority priority_of_order; 
    private User sender; 
    private Location destination; 
    private PaymentDetails paymentDetails; 
    private List<Item> items; 
    private Long totalWeight; 
    private OrderStatus currentStatus; 
    private Date timeOfOrderPlaced; 
    private Date timeOfOrderDelivery; 
    private Vehicle vehicleOfThisOrder; 
  
    public int getOrderId() 
    { 
        return orderId; 
    } 
  
    public void setOrderId(int orderId) 
    { 
        this.orderId = orderId; 
    } 
  
    public OrderPriority getPriority_of_order() 
    { 
        return priority_of_order; 
    } 
  
    public void setPriority_of_order(OrderPriority priority_of_order) 
    { 
        this.priority_of_order = priority_of_order; 
    } 
  
    public User getSender() 
    { 
        return sender; 
    } 
  
    public void setSender(User sender) 
    { 
        this.sender = sender; 
    } 
  
    public Location getDestination() 
    { 
        return destination; 
    } 
  
    public void setDestination(Location destination) 
    { 
        this.destination = destination; 
    } 
  
    public PaymentDetails getPaymentDetails() 
    { 
        return paymentDetails; 
    } 
  
    public void setPaymentDetails(PaymentDetails paymentDetails) 
    { 
        this.paymentDetails = paymentDetails; 
    } 
  
    public List<Item> getItems() 
    { 
        return items; 
    } 
  
    public void setItems(List<Item> items) 
    { 
        this.items = items; 
    } 
  
    public Long getTotalWeight() 
    { 
        return totalWeight; 
    } 
  
    public void setTotalWeight(Long totalWeight) 
    { 
        this.totalWeight = totalWeight; 
    } 
  
    public OrderStatus getCurrentStatus() 
    { 
        return currentStatus; 
    } 
  
    public void setCurrentStatus(OrderStatus currentStatus) 
    { 
        this.currentStatus = currentStatus; 
    } 
  
    public Date getTimeOfOrderPlaced() 
    { 
        return timeOfOrderPlaced; 
    } 
  
    public void setTimeOfOrderPlaced(Date timeOfOrderPlaced) 
    { 
        this.timeOfOrderPlaced = timeOfOrderPlaced; 
    } 
  
    public Date getTimeOfOrderDelivery() 
    { 
        return timeOfOrderDelivery; 
    } 
  
    public void setTimeOfOrderDelivery(Date timeOfOrderDelivery) 
    { 
        this.timeOfOrderDelivery = timeOfOrderDelivery; 
    } 
  
    public Vehicle getVehicleOfThisOrder() 
    { 
        return vehicleOfThisOrder; 
    } 
  
    public void setVehicleOfThisOrder(Vehicle vehicleOfThisOrder) 
    { 
        this.vehicleOfThisOrder = vehicleOfThisOrder; 
    } 
} 

The main class (LogisticsSystem) which stores all the information of users, orders and vehicles. It has the methods like takeAnOrder(), processOrder() etc.

import java.util.ArrayList; 
import java.util.List; 
  
public class LogisticsSystem { 
  
    private List<Order> orders; 
    private List<Vehicle> vehicles; 
    private List<User> users; 
  
    public LogisticsSystem() 
    { 
        this.orders = new ArrayList<Order>(); 
        this.vehicles = new ArrayList<Vehicle>(); 
        this.users = new ArrayList<User>(); 
    } 
  
    public void takeAnOrder(Order order) 
    { 
        System.out.println("Adding an order to the system"); 
        orders.add(order); 
    } 
  
    public void processOrder(Order order) 
    { 
        System.out.println("Processing an order of the system"); 
    } 
  
    public Location trackOrder(int orderId) 
    { 
        System.out.println("Tracking an order of the system"); 
        Location location = null; 
        // location = findLocationOfGivenOrder(); 
        return location; 
    } 
  
    public void cacelOrder(Order order) 
    { 
        System.out.println("Going to cancell an order of the system"); 
    } 
  
    public void registerNewUser(User user) 
    { 
        System.out.println("Registering a new user to the system"); 
        users.add(user); 
    } 
  
    public List<Order> getOrders() 
    { 
        return orders; 
    } 
  
    public void setOrders(List<Order> orders) 
    { 
        this.orders = orders; 
    } 
  
    public List<Vehicle> getVehicles() 
    { 
        return vehicles; 
    } 
  
    public void setVehicles(List<Vehicle> vehicles) 
    { 
        this.vehicles = vehicles; 
    } 
  
    public List<User> getUsers() 
    { 
        return users; 
    } 
  
    public void setUsers(List<User> users) 
    { 
        this.users = users; 
    } 
} 

This is the test class to test the application.

package com.shashi.oodesign; 
  
import java.util.ArrayList; 
import java.util.Date; 
import java.util.List; 
  
public class Apptest { 
  
    public static void main(String[] args) 
    { 
  
        User user = new User(); 
        user.setUserId(1); 
        user.setName("Shashi"); 
        user.setEmailId("shashi@gmail.com"); 
  
        Item item1 = new Item(); 
        item1.setName("item1"); 
        item1.setPrice(20); 
  
        Item item2 = new Item(); 
        item2.setName("item2"); 
        item2.setPrice(40); 
  
        List<Item> items = new ArrayList<Item>(); 
        items.add(item1); 
        items.add(item2); 
  
        PaymentDetails paymentDetails = new PaymentDetails(); 
        paymentDetails.setAmount(100); 
        paymentDetails.setPaymentMode(PaymentMode.CREDIT_CARD); 
        paymentDetails.setCardNumber("12345678"); 
  
        Location destination = new Location(); 
        destination.setLatitude(73.23); 
        destination.setLongitude(132.34); 
  
        Order order = new Order(); 
        order.setOrderId(1); 
        order.setItems(items); 
        order.setCurrentStatus(OrderStatus.PROCESSING); 
        order.setDestination(destination); 
        order.setPaymentDetails(paymentDetails); 
        order.setTimeOfOrderDelivery(new Date()); 
  
        LogisticsSystem logisticsSystem = new LogisticsSystem(); 
        logisticsSystem.registerNewUser(user); 
        logisticsSystem.takeAnOrder(order); 
        logisticsSystem.processOrder(order); 
    } 
} 

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