A simple ATM Machine project built in Java to demonstrate the State Design Pattern as part of a Software Engineering assignment. The ATM changes behavior based on its current state — NoCard, HasCard, and Authenticated — following clean object-oriented design principles.

Features:

• Implements the State Pattern

• Three ATM states:

NoCardState

HasCardState

AuthenticatedState

• Context class (ATM.java) that delegates actions to states

• Supports operations:

Insert card

Enter PIN

Withdraw cash

• Includes unit tests and a simple star-pattern output utility

• Organized as one-class-per-file following Java coding conventions

State Design Pattern Overview:

This project demonstrates how behavior changes dynamically at runtime based on internal state.

State Pattern Benefits:

Removes large if-else / switch blocks

Each state encapsulates its own logic

Increases code readability

Easy to extend new states

📁 Project Structure ATMMachine/ ├── ATM.java (Context class) ├── State.java (Interface for common actions) ├── NoCardState.java (State when no card is inserted) ├── HasCardState.java (State when card is inserted) ├── AuthenticatedState.java (State after correct PIN) ├── ATMTests.java (Unit tests) ├── StarPattern.java (Simple star pattern output) └── README.md (Project description)

🧪 Unit Tests

Two lightweight tests validate:

✔ State transitions ✔ Action behavior under each state ✔ Star pattern generation (bonus test)