Code for the Amazon Locker Service

We've gone over the different aspects of the Amazon Locker service and observed the attributes attached to the problem using various UML diagrams. Let’s explore the more practical side of things, where we will work on implementing the Amazon Locker service using multiple languages. This is usually the last step in an object-oriented design interview process.

We have chosen the following languages to write the skeleton code of the different classes present in the Amazon Locker service:

Java
C#
Python
C++
JavaScript

Amazon Locker service classes#

In this section, we will provide the skeleton code of the classes designed in the class diagram lesson.

Note: For simplicity, we are not defining getter and setter functions. The reader can assume that all class attributes are private and accessed through their respective public getter methods and modified only through their public method functions.

Enumerations#

First, we will define all the enumerations used in the Amazon Locker service. According to the class diagram, there are two enumerations in the system, i.e., LockerSize and LockerState The code to implement these enumerations is as follows:

Note: JavaScript does not support enumerations, so we will be using the Object.freeze() method as an alternative that freezes an object and prevents further modifications.

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Constant definitions

public class Package {
  private String packageId;
  private double packageSize;
  private Order order;
  public void pack();
}
public class LockerPackage extends Package {
  private int codeValidDays;
  private String lockerId;
  private String packageId;
  private String code;
  private Date packageDeliveryTime;
  public boolean isValidCode();
  public boolean verifyCode(String code);
}

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The Package and LockerPackage classes

public class Locker {
  private String lockerId;
  private LockerSize lockerSize;
  private String locationId;
  private LockerState lockerState;
  public boolean addPackage();
  public boolean removePackage();
}
public class LockerLocation {
  private String name;
  private List<Locker> lockers;
  private double longitude;
  private double latitude;
  private Date openTime;
  private Date closeTime;
}

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The Locker and LockerLocation classes

public class LockerService {
    private List<LockerLocation> locations;
    // The LockerService is a Singleton class that ensures it will have only one active instance at a time
    private static LockerService lockerService = null;
    
    // Created a static method to access the Singleton instance of LockerService class
    public static LockerService getInstance() {
        if (lockerService == null) {
            lockerService = new LockerService();
        }
        return lockerService;
    }
}
public class Notification {
    private String customerId;
    private String orderId;
    private String lockerId;
    private String code;
    public void send();
}

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The LockerService and Notification classes

Amazon Locker service classes#

Enumerations#

Item and Order#

Package and LockerPackage#

Locker and LockerLocation#

LockerService and Notification#

Wrapping up#