What is DRY Principle ?

DRY Stands for -> Don't Repeat Yourself

It means that you should not repeat the same code over and over again. Instead, you should use functions or classes to reuse the code. Here's an example to help explain it:

Example 1:

Imagine you're building a website for a library. On the website, you have a page that shows a list of all the books in the library. You also have a page that shows a list of all the movies in the library. And you have a page that shows a list of all the music albums in the library.

If you're not following the DRY principle, you might write separate code for each of these pages to display the list of books, movies, and music albums. But that's a lot of repeating code, because the basic idea is the same for all three pages - they all show a list of items.

Instead, you should create a class, say Item, which will have all the properties and functions related to the items. And then you can create different objects of the class Book, Movie, Music etc.

So, you create a single class "Item" that has the code to display a list of items. And then you create different objects of the class for books, movies, and music albums. This way, you only have to write the code for displaying a list of items once, and you can reuse it for all three pages.

Example 2: The DRY principle is a programming principle that says "Don't Repeat Yourself." It means that you should avoid writing the same code multiple times in your program.

Here's an example to help explain it:

Let's say you have a program that checks if a number is even or odd. Without following the DRY principle, you might write the following code:

public class Main {
    public static void main(String[] args) {
        int num1 = 5;
        if (num1 % 2 == 0) {
            System.out.println(num1 + " is even");
        } else {
            System.out.println(num1 + " is odd");
        }
 
        int num2 = 6;
        if (num2 % 2 == 0) {
            System.out.println(num2 + " is even");
        } else {
            System.out.println(num2 + " is odd");
        }
    }
}

As you can see here, the logic to check if number is even or odd is repeating.

Instead, you can write a function that takes a number as input, checks if it's even or odd, and prints the result. And then call that function for each number you want to check.

public class Main {
   public static void checkEvenOdd(int num) {
       if (num % 2 == 0) {
           System.out.println(num + " is even");
       } else {
           System.out.println(num + " is odd");
       }
   }
 
   public static void main(String[] args) {
       checkEvenOdd(5);
       checkEvenOdd(6);
   }
}

In this way you only write the logic once and use it multiple times, avoiding repetition of code.