SRP vs Separation of Concerns in Java

Direct Answer

Separation of Concerns is the broad idea of organizing a system so distinct concerns are handled in distinct parts, from modules and layers down to functions. SRP is a more specific change-oriented principle: a class or module should be responsible to one main actor or cohesive concern. They support each other but are not simply architecture versus classes.

Code Example

@RestController
final class OrderController {          // HTTP translation concern
    private final PlaceOrder useCase;

    OrderController(PlaceOrder useCase) { this.useCase = useCase; }
}

final class PlaceOrder {               // order-use-case responsibility
    private final OrderRepository orders;
    private final PaymentGateway payments;
}

interface OrderRepository {            // persistence port
    void save(Order order);
}

The layers demonstrate separation of concerns. SRP is evaluated separately inside each class or module by asking which actor or policy makes it change.

Common Mistakes & Pitfalls

• Reducing the distinction to architecture versus classes: both ideas can apply at several scales.
• Trusting layer names: a service package can still contain mixed policies.
• Equating more folders with better separation: boundaries should reduce real coupling and change collisions.
• Fragmenting cohesive behavior: keep code together when it changes for the same reason.