Jordan’s Virtual Bank

“Real Money. Real Logic. Real OOP.”

Jordan just got serious about managing money.

He has:

• A Checking Account
• A Savings Account (earns interest)
• One additional account type of your choice

Your job is to build his virtual banking system using proper Object-Oriented Programming principles.

This is not a “just make it work” assignment. This is a prove you understand OOP assignment.

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Objective

Design a small banking system that demonstrates:

• Abstraction
• Encapsulation
• Inheritance
• Polymorphism

If you cannot explain where each principle appears in your code, you did not complete the assignment correctly.

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Required Files

You must create:

• BankAccount.java
• CheckingAccount.java
• SavingsAccount.java
• YourThirdAccountType.java
• Main.java

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System Requirements

Base Account

Create a base account class that represents what all accounts have in common.

All accounts must:

• Have an owner
• Have an account number
• Have a balance
• Support deposits
• Support withdrawals
• Support a monthly update
• Be able to print a summary

Not all accounts behave the same way.

That’s intentional.

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Checking Account

• Allows deposits

• Allows withdrawals (cannot withdraw more than balance)

• Monthly update:

  • Apply a fee if balance is below a certain amount

You decide reasonable rules.

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Savings Account

• Allows deposits
• Allows withdrawals (cannot exceed balance)
• Must accrue interest during monthly update

You decide how interest works.

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Third Account (Your Choice)

Choose something different. Examples:

• Credit account
• Investment account
• High-yield savings
• Crypto wallet
• Business account

It must:

• Behave differently than checking and savings
• Have unique rules
• Override behavior where necessary

Be creative — but keep it realistic.

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Main Program Requirements

In Main.java:

1. Create at least one of each account type.
2. Store them together in a single collection (array or ArrayList).
3. Perform multiple transactions.
4. Run monthly updates on all accounts.
5. Print account summaries before and after updates.

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OOP Expectations

Your code must clearly demonstrate:

Abstraction

There should be behavior defined that subclasses must implement.

Encapsulation

Fields must not be publicly accessible. Validation must happen inside methods.

Inheritance

Account types must reuse shared behavior.

Polymorphism

You must treat different account types as the same base type at some point in your program.

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Restrictions

• No static global balances.
• No public fields.
• No copy-pasting code between account classes.
• No giant if(type == "...") statements in Main to control behavior.
• Do not hardcode behavior in Main that belongs in a class.

If your Main file controls account logic, you misunderstood the assignment.

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Minimum Output Example (Structure Only)

Your output should resemble:

--- BEFORE MONTHLY UPDATE ---
Checking (001) - Balance: $500.00
Savings (002) - Balance: $1000.00
Credit (003) - Balance: $300.00

--- AFTER MONTHLY UPDATE ---
Checking (001) - Balance: $495.00
Savings (002) - Balance: $1020.00
Credit (003) - Balance: $309.00

Your numbers will differ depending on your rules.

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Submission Rules

Be prepared to:

• Explain where each OOP principle exists in your code. Using comments
• Explain why you made certain methods abstract.
• Explain why fields are private.
• Explain how polymorphism works in your loop.

If you cannot explain it, you don’t fully understand it yet.

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Bonus (Optional)

Choose one:

• Add a transfer method between accounts
• Add transaction history
• Add overdraft logic
• Add user input with Scanner
• Add unit tests

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