Code Decoupling and Modularization in Java

// Coupled code
class AreaCalculator {
    public double calculateArea(double length, double width, String shape) {
        if (shape.equals("rectangle")) {
            return length * width; // calculate area for rectangle
        } else if (shape.equals("triangle")) {
            return (length * width) / 2; // calculate area for triangle
        }
        return 0;
    }
}

// Decoupled code
class RectangleAreaCalculator {
    public double calculateRectangleArea(double length, double width) {
        return length * width; // function to calculate rectangle area
    }
}

class TriangleAreaCalculator {
    public double calculateTriangleArea(double length, double width) {
        return (length * width) / 2; // function to calculate triangle area
    }
}

// Monolithic code with high dependencies
public class Order {
    private String[] items;
    private double[] prices;
    private double discountRate;
    private double taxRate;

    public Order(String[] items, double[] prices, double discountRate, double taxRate) {
        this.items = items;
        this.prices = prices;
        this.discountRate = discountRate;
        this.taxRate = taxRate;
    }

    public double calculateTotal() {
        double total = 0;
        for(double price : prices) {
            total += price;
        }
        total -= total * discountRate;
        total += total * taxRate;
        return total;
    }

    public void printOrderSummary() {
        double total = calculateTotal();
        System.out.printf("Order Summary: Items: %s, Total after tax and discount: $%.2f%n",
            String.join(", ", items), total);
    }
}

// Decoupled and modularized code
class DiscountCalculator {
    public static double applyDiscount(double price, double discountRate) {
        return price - (price * discountRate);
    }
}

class TaxCalculator {
    public static double applyTax(double price, double taxRate) {
        return price + (price * taxRate);
    }
}

public class Order {
    private String[] items;
    private double[] prices;
    private double discountRate;
    private double taxRate;

    public Order(String[] items, double[] prices, double discountRate, double taxRate) {
        this.items = items;
        this.prices = prices;
        this.discountRate = discountRate;
        this.taxRate = taxRate;
    }

    public double calculateTotal() {
        double total = 0;
        for(double price : prices) {
            total += price;
        }
        total = DiscountCalculator.applyDiscount(total, discountRate);
        total = TaxCalculator.applyTax(total, taxRate);
        return total;
    }

    public void printOrderSummary() {
        double total = calculateTotal();
        System.out.printf("Order Summary: Items: %s, Total after tax and discount: $%.2f%n",
            String.join(", ", items), total);
    }
}