6.2 Class, Object & Constructors

public class BankAccount {
    // 1. Instance Variables (State)
    private String accountNumber;
    private String accountHolderName;
    private double balance;

    // 2. Default Constructor
    public BankAccount() {
        this("ACC-000", "Guest User", 0.0); // Constructor Chaining using this()
    }

    // 3. Parameterized Constructor
    public BankAccount(String accountNumber, String accountHolderName, double initialBalance) {
        this.accountNumber = accountNumber;
        this.accountHolderName = accountHolderName;
        this.balance = initialBalance;
    }

    // 4. Methods (Behavior)
    public void deposit(double amount) {
        if (amount > 0) {
            this.balance += amount;
            System.out.println("₹" + amount + " जमा किए गए। नया बैलेंस: ₹" + this.balance);
        }
    }

    public void displayInfo() {
        System.out.println("खाता संख्या: " + this.accountNumber + " | धारक: " + this.accountHolderName + " | बैलेंस: ₹" + this.balance);
    }

    public static void main(String[] args) {
        // new कीवर्ड हीप में नया ऑब्जेक्ट बनाता है
        BankAccount acc1 = new BankAccount("SBI-1001", "Ahmad", 25000.0);
        BankAccount acc2 = new BankAccount("HDFC-2002", "Pooja", 50000.0);

        acc1.displayInfo();
        acc2.displayInfo();

        acc1.deposit(5000.0);
    }
}

    STACK MEMORY                     HEAP MEMORY
+--------------------+        +-----------------------------------+
| acc1 (Reference)   | -----> | BankAccount Object @101           |
| (Holds Address 101)|        | - accountNumber: "SBI-1001"       |
+--------------------+        | - accountHolderName: "Ahmad"      |
| acc2 (Reference)   | -----> | - balance: 30000.0                |
| (Holds Address 202)|        +-----------------------------------+
+--------------------+        | BankAccount Object @202           |
                              | - accountNumber: "HDFC-2002"      |
                              | - accountHolderName: "Pooja"      |
                              | - balance: 50000.0                |
                              +-----------------------------------+