Console Applications

A collection of robust, production-grade console applications built to demonstrate core Java fundamentals, object-oriented design, algorithmic business logic, and efficient data structuring.

Projects Overview

1. Library Management System

A feature-rich console application designed to handle end-to-end library workflows, featuring a highly automated Fine Engine and modular user access control.

• Architecture: Developed a multi-portal architecture separating concerns into Admin, User, and Explore modules, driven by a centralized static data layer.
• Core Functionality: Enabled interactive genre-based book discovery, a virtual shopping cart with real-time limit enforcement, and dynamic transaction tracking (borrow/return/lost logs).
• Advanced Fine Engine: Engineered complex penalty logic handling standard 15-day timelines, daily flat rates, and automated exponential penalty scaling (doubling every $X$ days) with security deposit deductions.

Credentials:

• Admin: venkat@gmail.com | Password: 1234
• User: sanjay@gmail.com | Password: 1234

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2. Automated Teller Machine (ATM) Simulation

A secure, high-fidelity command-line simulation of an ATM network validating real-time financial restrictions and state-locking mechanisms.

• Architecture: Utilizes a centralized data hub acting as a "Single Source of Truth" with map-based architectures for fast lookups and transaction list logging.
• Security Constraints: Implemented automated 24-hour security lockouts triggered after 3 consecutive invalid PIN entry attempts.
• Financial Operations: Automated strict logic workflows for account balance checking, PIN changes, deposit reserves tracking, and strict currency denomination validation (multiples of 100).
• Admin Portal: Equipped with administrative workflows for manual account suspension, user onboarding validation, full financial auditing logs, and reserve liquidity tracking.

Credentials:

• Admin: venkat123 | PIN: 1234
• User: sanjay123 | PIN: 1234

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Technical Highlights & Competencies

• Java Collections Framework: Heavily leveraged HashMap structures for optimized $O(1)$ lookup times and TreeMap for natural-order data sorting.
• Robust Input Validation: Standardized application uptime by integrating comprehensive try-catch blocks for InputMismatchException to elegantly handle erratic user input.
• Date-Time API Integration: Automated precise temporal calculations using Java 8 LocalDate and ChronoUnit frameworks to calculate borrow aging and deadlines.
• State Management: Emulated cross-session relational integrity utilizing memory-resident mockup datastores.

Prerequisites & Installation

Java Development Kit (JDK) 8 or higher installed.