Open-Closed Principle

The Open-Closed Principle states that:

Software entities (classes, modules, functions, etc) should be open for extension, but closed for modification.

This principle basically states that we have to design our modules, classes, and functions in a way that when a new functionality is needed, we should not modify our existing code but rather write new code that will be used by existing code

Now let us discuss the Open-Closed Principle in the following example.

Let us assume we are trying to calculate the area of some shapes. So let's take the example of a rectangle and a circle. The classes for these have been formed in the following code:

public class Rectangle { 
   private double length; 
   private double height; 
   // getters/setters ... 
} 
 
public class Circle { 
   private double radius; 
   // getters/setters ... 
} 

So a common function used...