Class Methods & Challenge

Instance methods use object data: void deposit(double amount). Static methods belong to class: Math.max style.

Methods — behavior inside classes

Instance methods use object data: void deposit(double amount). Static methods belong to class: Math.max style.

Call instance method on object: acc.deposit(100). Call static on class: Demo.calculate().

Real-life example: deposit() is something one bank account does. calculateTax() might be a static tool for all accounts.

Instance and static methods

class BankAccount {
    double balance = 0;

    void deposit(double amount) {
        if (amount > 0) balance += amount;
    }

    static double interestRate() {
        return 4.5;
    }
}

Challenge — build a Product class

Create Product with name, price, quantity. Add methods applyDiscount(percent), restock(amount), getTotalValue().

Create two Product objects in main and call each method.

Real-life example: Challenge is like building a mini shop shelf in code — one product class, many products on shelf.

Challenge: Add a method isLowStock() that returns true when quantity < 5.