Learn Applying DRY | Fundamental Coding Principles

Introduction to DRY (Don't Repeat Yourself)

The DRY (Don't Repeat Yourself) principle is a core concept in software development that encourages you to avoid duplicating code or logic. By following DRY, you aim to write each piece of knowledge or logic only once within your codebase. This approach helps you:

Improve code maintainability;
Reduce the risk of errors caused by inconsistent changes;
Make updates and bug fixes faster and easier;
Enhance code readability and clarity for yourself and others.

Applying the DRY principle leads to cleaner, more efficient code that is easier to manage as your projects grow. Instead of copying and pasting similar code, you create reusable methods, classes, or modules, ensuring each concept has a single, clear representation in your application.

Real-World Development Example

Imagine you need to calculate the area of multiple rectangles in your Java application. Instead of writing the multiplication logic for each rectangle separately, you can centralize this calculation in a single method. This method can then be reused anywhere you need to compute a rectangle's area. By doing so, you avoid code duplication, make your program easier to maintain, and follow the DRY (Don't Repeat Yourself) principle.

Main.java


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package com.example;

public class Main {
    public static void main(String[] args) {
        double length1 = 5.0;
        double width1 = 3.0;
        double length2 = 7.5;
        double width2 = 4.2;

        double area1 = RectangleUtils.calculateArea(length1, width1);
        double area2 = RectangleUtils.calculateArea(length2, width2);

        System.out.println("Area of rectangle 1: " + area1);
        System.out.println("Area of rectangle 2: " + area2);
    }
}

class RectangleUtils {
    // This method applies DRY by centralizing the area calculation logic
    public static double calculateArea(double length, double width) {
        return length * width;
    }
}

What the Code Does

Defines a class DiscountCalculator with a method calculateDiscountedPrice.
The calculateDiscountedPrice method takes originalPrice and discountPercentage as parameters and returns the discounted price.
The main method calls calculateDiscountedPrice multiple times with different values, printing the results for each product.

How This Demonstrates DRY

Avoids duplication: Instead of writing the discount calculation formula separately for each product, the logic is written once inside calculateDiscountedPrice.
Improves maintainability: If you need to update the discount logic, you only change it in one place.
Increases readability: The code is easier to read and understand because the discount calculation is clearly separated and named.
Encourages reuse: You can reuse the calculateDiscountedPrice method for any product, making your code more flexible and scalable.

By centralizing repeated logic, you reduce errors and make future changes easier, which is the core of the DRY principle in software development.

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