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public class BankAccount {
    // Fields (instance variables)
    private String owner;
    private double balance;
    private static int totalAccounts = 0;  // shared across all instances

    // Constructor
    public BankAccount(String owner, double initialBalance) {
        this.owner = owner;
        this.balance = initialBalance;
        totalAccounts++;
    }

    // Getter methods
    public String getOwner() { return owner; }
    public double getBalance() { return balance; }

    // Business methods
    public void deposit(double amount) {
        if (amount <= 0) throw new IllegalArgumentException("Amount must be positive");
        balance += amount;
    }

    public boolean withdraw(double amount) {
        if (amount > balance) return false;
        balance -= amount;
        return true;
    }

    // Static method
    public static int getTotalAccounts() { return totalAccounts; }

    // toString for readable output
    @Override
    public String toString() {
        return owner + ": $" + String.format("%.2f", balance);
    }
}

// Usage
public class Main {
    public static void main(String[] args) {
        BankAccount acc = new BankAccount("Alice", 1000);
        acc.deposit(500);
        acc.withdraw(200);
        System.out.println(acc);  // Alice: $1300.00
        System.out.println(BankAccount.getTotalAccounts());  // 1
    }
}

public class Product {
    private String name;
    private double price;
    private int quantity;

    // Primary constructor
    public Product(String name, double price, int quantity) {
        this.name = name;       // this disambiguates field from parameter
        this.price = price;
        this.quantity = quantity;
    }

    // Overloaded constructor — delegates to primary using this()
    public Product(String name, double price) {
        this(name, price, 0);   // calls the 3-param constructor
    }

    // Copy constructor
    public Product(Product other) {
        this(other.name, other.price, other.quantity);
    }
}

// A record auto-generates constructor, getters, equals, hashCode, toString
public record Point(double x, double y) {
    // Compact constructor for validation
    public Point {
        if (x < 0 || y < 0) throw new IllegalArgumentException("Negative coords");
    }

    // Custom method
    public double distanceTo(Point other) {
        return Math.sqrt(Math.pow(this.x - other.x, 2) + Math.pow(this.y - other.y, 2));
    }
}

// Usage — clean, immutable value object
Point p1 = new Point(0, 0);
Point p2 = new Point(3, 4);
System.out.println(p1.distanceTo(p2));  // 5.0
System.out.println(p1);                  // Point[x=0.0, y=0.0]