Real World Analogies and Code Example

In the previous lesson, we learned the definition of the Open/Closed Principle (OCP). Now, in this lesson, we’ll explore a real-world coding example to understand how this principle is applied.

Initial Code Example Without OCP

Let’s start with a code example where all methods and logic are placed within a single class. This approach violates the Open/Closed Principle because adding new functionality will require us to modify the existing class.

In this example, the Invoice class is responsible for generating invoices and applying discounts

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Keshav Garg

· 2 years ago

 public class Invoice {
    private double amount;

    public Invoice(double amount) {
        this.amount = amount;
    }

    public double getAmount() {
        return amount;
    }

    // This method handles generating basic invoices
    public void generateInvoice() {
        System.out.println("Generating basic invoice for amount: " + amount);
    }

    // This method handles applying discounts on the invoice
    public void applyDiscount() {
        System.out.println("Applying discount on invoice: " + amount);
    }
}

public class InternationalInvoice extends Invoice {
	@Override
	public void generateInvoice() {
			System.out.println("Generating International invoice for amount: " + amount);
	}
}

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