Can you explain the concept of low coupling of system components?

Loose coupling means that system components depend on each other minimally. This increases flexibility, makes maintenance and testing easier.

In the context of Java, this can mean:

• Using interfaces instead of concrete classes for interaction.
• Applying inversion of control (IoC) and dependency injection (DI) so that components do not create each other directly.
• Exchanging data through well-defined APIs or messages, rather than direct access to internal data.

Example:

public interface PaymentService {
    void pay(double amount);
}

public class PaypalPaymentService implements PaymentService {
    public void pay(double amount) {
        // implementation of PayPal payment
    }
}

public class OrderProcessor {
    private PaymentService paymentService;

    public OrderProcessor(PaymentService paymentService) {
        this.paymentService = paymentService;
    }

    public void processOrder(double amount) {
        paymentService.pay(amount);
    }
}

Here, OrderProcessor depends on the abstraction PaymentService, not on a specific implementation, which reduces coupling.