onlineauctionsystem

Online Auction System (LLD)

Problem Statement

Design and implement an Online Auction System that allows users to create auctions, place bids on items, track auction status, and determine winners.

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Requirements

• User Management: Users can register and participate in auctions.
• Item Management: The system manages items that can be auctioned.
• Auction Creation: Users can create auctions for items, specifying start and end times.
• Bidding: Users can place bids on active auctions.
• Auction Status Tracking: The system tracks the status of each auction (e.g., ACTIVE, ENDED).
• Winner Determination: The system determines the winning bid and user when an auction ends.
• Extensibility: Easy to add new features such as reserve prices, buy-now options, or notifications.

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Core Entities

• AuctionSystem: Main class that manages users, items, auctions, and bidding.
• User: Represents a user who can create auctions and place bids.
• Item: Represents an item to be auctioned.
• Auction: Represents an auction for an item, including bids, status, and winner.
• Bid: Represents a bid placed by a user on an auction.
• AuctionStatus: Enum for auction status (ACTIVE, ENDED).

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Class Design

UML Class Diagram

1. AuctionSystem

• Fields: List users, List items, List auctions
• Methods: registerUser(User), addItem(Item), createAuction(Item, User, Date startTime, Date endTime), placeBid(Auction, User, double amount), endAuction(Auction), getActiveAuctions(), getEndedAuctions(), etc.

2. User

• Fields: int id, String name

3. Item

• Fields: int id, String name, String description

4. Auction

• Fields: int id, Item item, User seller, List bids, AuctionStatus status, User winner, Date startTime, Date endTime
• Methods: addBid(Bid), endAuction(), getHighestBid(), getWinner()

5. Bid

• Fields: int id, User bidder, double amount, Date bidTime

6. AuctionStatus (enum)

• Values: ACTIVE, ENDED

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Example Usage

AuctionSystem system = new AuctionSystem();
User alice = new User(1, "Alice");
User bob = new User(2, "Bob");
system.registerUser(alice);
system.registerUser(bob);

Item painting = new Item(1, "Painting", "Beautiful landscape painting");
system.addItem(painting);

Auction auction = system.createAuction(painting, alice, new Date(), new Date(System.currentTimeMillis() + 3600000));
system.placeBid(auction, bob, 100.0);
system.placeBid(auction, alice, 120.0);

system.endAuction(auction);
User winner = auction.getWinner();
System.out.println("Winner: " + (winner != null ? winner.getName() : "No winner"));

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Demo

See AuctionSystemDemo.java for a sample usage and simulation of the online auction system.

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Extending the Framework

• Add reserve prices: Only sell if the highest bid meets the minimum price.
• Add buy-now options: Allow instant purchase at a set price.
• Add notifications: Notify users of auction events or outbids.

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