Single Responsibility Principle (SRP) – Complete Guide

What is SRP?

The Single Responsibility Principle (SRP) is a core concept in SOLID programming. It states that every class or module should have only one responsibility, meaning only one reason to change. Following SRP makes code easier to maintain, test, and extend.

Why SRP is Important

• Reduces complexity and coupling.
• Makes code easier to read and maintain.
• Facilitates testing and debugging.
• Prevents unintended side effects when changing code.

Stepwise Implementation of SRP

1. Step 1 – Identify Responsibilities: Review your class or module to see all tasks it performs.
2. Step 2 – Separate Responsibilities: Divide the tasks into different logical responsibilities.
3. Step 3 – Create Single Responsibility Classes: Assign each responsibility to a dedicated class.
4. Step 4 – Refactor Code: Move relevant methods and data to the new classes.
5. Step 5 – Test Functionality: Ensure each class performs its single task correctly.

Example: SRP in Action

Suppose we have an application that needs to:

• Send emails
• Fetch employee data
• Calculate salaries

Instead of one class handling all three, we separate responsibilities:

class EmailSender {
    public void sendEmail(String recipient, String message) {
        // logic to send email
    }
}

class DataFetcher {
    public Employee getEmployeeData(int id) {
        // logic to fetch employee data
    }
}

class SalaryCalculator {
    public double calculateSalary(Employee emp) {
        // logic to calculate salary
    }
}
      

This way, each class has a single responsibility. Modifying email logic won’t affect salary calculation or data fetching.