The Single Responsibility Principle (SRP) is a fundamental principle of software design that states that a class or module should have only one reason to change. This means that each class or module should have a single, well-defined responsibility, and that responsibility should be encapsulated by the class or module.

The goal of SRP is to make the design of a system more maintainable and flexible by dividing it into smaller, more manageable parts. By limiting the scope of each class or module, developers can make changes to the system with a reduced risk of affecting other parts of the system. This also makes it easier to understand the purpose and behavior of each class or module, which in turn makes it easier to identify and fix problems.

Example

Here's an example of the Single Responsibility Principle in Java:

public class User {
    private String name;
    private String email;

    public User(String name, String email) {
        this.name = name;
        this.email = email;
    }

    public String getName() {
        return name;
    }

    public String getEmail() {
        return email;
    }
}

public class UserService {
    private List<User> users;

    public UserService() {
        this.users = new ArrayList<>();
    }

    public void addUser(User user) {
        users.add(user);
    }

    public List<User> getUsers() {
        return users;
    }
}

In this example, the User class has a single responsibility, which is to represent a user. The UserService class also has a single responsibility, which is to manage a list of users. This separation of responsibilities makes it easier to modify and maintain the system, since changes to one class or module will not affect the other. Additionally, this makes it easier to test and debug the system, since each class or module can be tested in isolation.