Vehicle Rental Agency. Lambdas and Streams

The purpose of this exercise is to check your knowledge of the Stream API and lambda expressions and your ability to use them to work with Java collections.

Duration: 1 hour

Description

In this exercise, you will implement "Vehicle Rental Agency" to allow users to filter and sort vehicles and information about orders in a variety of ways. The class diagram of the Domain model is shown in the figure below:

You are also given a description of the following interfaces and class:

• The Sort interface allows vehicles to be sorted by id, year of production, and odometer reading.
• The Find interface allows users to search for and filter vehicles and orders based on various criteria.
• The Agency class determines the functionality of the vehicle rental agency.

First, proceed to the Domain model classes and implement their content.
Then, proceed to the Agency class, which contains lists of the Vehicle and Order types and implements the Sort and Find interfaces. You need to implement the following methods of the Agency class:

• public void addVehicle(Vehicle vehicle)
  Adds a vehicle to a list of vehicles

• public void addOrder(Order order)
  Adds an order to a list of orders

• Set<String> findMakers()
  Returns a set of the vehicle makes the agency has in its fleet

• Set<BodyType> findBodytypes()
  Returns a set of the body types of the vehicles the agency has in its fleet

• Map<String, List<Vehicle>> findVehicleGrouppedByMake()
  Returns a map in which the key is the make of the vehicle, and the value is a list of the vehicles of a given make that the agency has in its fleet

• List<Client> findTopClientsByPrices(List<Client> clients, int maxCount)
  Calculates the total order amount for each client and then returns the maxCount of the clients with the highest amount. If the total number of clients is less than maxCount, a list of all the clients is returned.

• List<Client> findClientsWithAveragePriceNoLessThan(List<Client> clients, int average)
  Calculates the average number of orders for each client and returns a list of clients whose average order amount is not less than average

• List<Vehicle> findMostOrderedVehicles(int maxCount)
  Calculates how many times each vehicle in the fleet has been ordered and then returns the maxCount of the vehicles ordered most frequently. If the total number of vehicles is less than maxCount, a list of all the vehicles is returned.

• List<Vehicle> sortByID()
  Returns all vehicles sorted by id as a new list

• List<Vehicle> sortByYearOfProduction()
  Returns all vehicles sorted by yearOfProduction as a new list

• List<Vehicle> sortByOdometer() Returns all vehicles sorted by odometer as a new list

Note: When implementing the methods of the Find and Sort interfaces, you must use the Stream API and lambda expressions.

Details

• Domain model classes must have the following:
  • A default constructor
  • A constructor that takes values to initialize all fields as parameters
  • Getters and setters for all fields
  • The equals(), hashCode(), and toString() methods

Note: In the future, it's expected that objects of these classes will be transferred over a network or stored in a file or database.

• The string representation of an object of these classes must follow the following convention:

  Class_name{field1_name=field_value,     field2_name=field_value, …}
  

  • If a class inherits another class, it must include inherited fields before its own fields:

  Class_name{parent_class_fields, own_fields}
  

  • String values must be surrounded by apostrophes. For example: text='value'
  • If a field is a collection or an array, its value must be surrounded by square brackets.
  • Fields must be ordered as denoted in the UML class diagram.

An example of a string representation

Let class A have the following description:

class A {
    private int p = 10;
    protected int a = 1;
    protected String s = "a string";
    // ...
}

The string representation of the object will be as follows:

A{p=10, a=1, s='a string'}

Let class B be the inheritor of class A and have the following description:

class B extends A {
    private int b = 5;
    private String t = "a text";
    private char[] chars = {'a', 'b'};
    // ...
}

The string representation of the object will be as follows:

B{a=1, s='a string', b=5, t='a text', chars=[a, b]}