Code for the Online Stock Brokerage System

Write the object-oriented code to implement the design of the ‘online stock brokerage system’ problem.

We'll cover the following

Online stock brokerage system classes
Wrapping up

We've reviewed different aspects of the online stock brokerage system 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 online stock brokerage system 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 online stock brokerage system:

Java
C#
Python
C++
JavaScript

Online stock brokerage system classes#

In this section, we’ll 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 and custom data type#

First of all, we will define all the enumerations required in the stock brokerage system. According to the class diagram, there are three enumerations used in the system i.e. OrderStatus, TimeEnforcementType and AccountStatus. The code to implement these enumerations and custom data types 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.

// Enumeration
enum OrderStatus {
  OPEN, 
  FILLED, 
  PARTIALLY_FILLED, 
  CANCELED
}
enum TimeEnforcementType {
  GOOD_TILL_CANCELED, 
  FILL_OR_KILL, 
  IMMEDIATE_OR_CANCEL, 
  ON_THE_OPEN,
  ON_THE_CLOSE
}
enum AccountStatus {
  ACTIVE, 
  CLOSED, 
  CANCELED, 
  BLACKLISTED, 
  NONE
}
// Custom Address data type class
public class Address {
  private int zipCode;
  private String address;
  private String city;
  private String state;
  private String country;

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Definition of enums and custom datatypes

// Account is an abstract class
public abstract class Account {
  private String id;
  private String password;
  private String name;
  private AccountStatus status;
  private Address address;
  private String email;
  private String phone;
  public abstract boolean resetPassword();
}
public class Member extends Account {
  private double availableFundsForTrading;
  private Date dateOfMembership;
  private HashMap<string, StockPosition> stockPositions;
  private HashMap<Integer, Order> activeOrders;
  public ErrorCode placeSellLimitOrder(string stockId, float quantity, int limitPrice, TimeEnforcementType enforcementType);
  public ErrorCode placeBuyLimitOrder(string stockId, float quantity, int limitPrice, TimeEnforcementType enforcementType);
  public void callbackStockExchange(int orderId, List<OrderPart> orderParts, OrderStatus status);
  public boolean resetPassword(){
    // definition
  }
}
public class Admin extends Account {
  public boolean blockMember();
  public boolean unblockMember();
  public boolean cancelMembership();

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Account and its child classes

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The Watchlist and the Stock classes

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The Search interface and the StockInventory class

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The StockPosition and StockLot classes

public class OrderPart {
  private double price;
  private double quantity;
  private Date executedAt;
}
// Order is an abstract class
public abstract class Order {
  private String orderNumber;
  public boolean isBuyOrder;
  private OrderStatus status;
  private TimeEnforcementType timeEnforcement;
  private Date creationTime;
  private HashMap<int, OrderPart> parts;
  public void setStatus(OrderStatus status);
  public boolean saveInDatabase();
  public void addOrderParts(OrderParts parts);
}
public class LimitOrder extends Order {
}
public class StopLimitOrder extends Order {
}
public class StopLossOrder extends Order {
}
public class MarketOrder extends Order {
}

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OrderPart, Order and its derived classes

// TransferMoney is an abstract class
public abstract class TransferMoney {
  private int id;
  private Date creationDate;
  public int fromAccount;
  private int toAccount;
  public abstract boolean initiateTransaction();
}
public class ElectronicBank extends TransferMoney {
  private String bankName;
  
  public boolean initiateTransaction(){
    // definition
  }
}
public class Wire extends TransferMoney {
  private int wire;
  public boolean initiateTransaction(){
    // definition
  }
}
public class Check extends TransferMoney {
  private String checkNumber;
  public boolean initiateTransaction(){
    // definition

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TransferMoney and its derived classes

public abstract class Notification {
    private String notificationId;
    private Date creationDate;
    private String content;
    public abstract boolean sendNotification();
}
public class SmsNotification extends Notification {
    private int phoneNumber;
    public boolean sendNotification(){
        // definition
    }
}
public class EmailNotification extends Notification {
    private String email;
    public boolean sendNotification(){
        // definition
    }
}

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Notification and its derived classes

public class StockExchange {
  // The StockExchange is a singleton class that ensures it will have only one active instance at a time
  private static StockExchange instance = null;
  // Created a private constructor to add a restriction (due to Singleton)
  private StockExchange() {}
  // Created a static method to access the singleton instance of StockExchange
  public static StockExchange getInstance()
  {
    if(instance == null) {
      instance = new StockExchange();
    }
    return instance;
  }
  public boolean placeOrder(Order order);
}

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The StockExchange class

Activity Diagram for the Online Stock Brokerage System

Getting Ready: Jigsaw Puzzle