online-auction-system.md

Designing an Online Auction System

In this article, we delve into the object-oriented design and implementation of an Online Auction System using Java.

This system allows for the creation and management of auctions, user participation in bidding, and handling transactions.

System Requirements

The Online Auction System should:

1. Auction Management: Create and manage auctions with item details, starting prices, and durations.
2. User Account Management: Handle user registrations for sellers and bidders.
3. Bidding Process: Allow users to place and track bids.
4. Auction Monitoring: Enable users to view ongoing auctions and status.
5. Transaction Processing: Handle winning bid transactions.

Core Use Cases

1. Creating and Managing Auctions
2. Registering and Managing User Accounts
3. Placing and Tracking Bids
4. Monitoring Auction Progress
5. Processing Transactions

Key Classes:

• OnlineAuctionSystem: Manages the system.
• User: Represents a system user.
• Auction: Manages auction details.
• Bid: Represents a user's bid.

Java Implementation

User Class

Manages user account information.

public class User {
    private String userId;
    private String name;
    private String email;

    public User(String userId, String name, String email) {
        this.userId = userId;
        this.name = name;
        this.email = email;
    }

    // Getters and setters...
}

Auction Class

Represents an auction.

import java.util.Date;
import java.util.HashMap;
import java.util.Map;

public class Auction {
    private String auctionId;
    private String itemDescription;
    private double startingPrice;
    private Date endTime;
    private User seller;
    private Map<User, Double> bids;

    public Auction(String auctionId, String itemDescription, double startingPrice, Date endTime, User seller) {
        this.auctionId = auctionId;
        this.itemDescription = itemDescription;
        this.startingPrice = startingPrice;
        this.endTime = endTime;
        this.seller = seller;
        this.bids = new HashMap<>();
    }

    public void placeBid(User bidder, double bidAmount) {
        bids.put(bidder, bidAmount);
    }

    // Getters and setters...
}

Bid Class

Represents a bid.

public class Bid {
    private User bidder;
    private double amount;

    public Bid(User bidder, double amount) {
        this.bidder = bidder;
        this.amount = amount;
    }

    // Getters and setters...
}

OnlineAuctionSystem Class

Manages the online auction system operations.

import java.util.ArrayList;
import java.util.List;

public class OnlineAuctionSystem {
    private List<User> users;
    private List<Auction> auctions;

    public OnlineAuctionSystem() {
        this.users = new ArrayList<>();
        this.auctions = new ArrayList<>();
    }

    public void addUser(User user) {
        users.add(user);
    }

    public void addAuction(Auction auction) {
        auctions.add(auction);
    }

    public void placeBid(String auctionId, User bidder, double bidAmount) {
        Auction auction = findAuctionById(auctionId);
        if (auction != null) {
            auction.placeBid(bidder, bidAmount);
        }
    }

    private Auction findAuctionById(String auctionId) {
        for (Auction auction : auctions) {
            if (auction.getAuctionId().equals(auctionId)) {
                return auction;
            }
        }
        return null; // No auction found with the given ID
    }

    // Other necessary methods...