Java With Us

Abstraction

Updated on 2026-04-21 Reviewed by the Java With Us editorial team

Abstraction is the principle of exposing only what a component does and hiding how it does it. In Java you achieve abstraction with interfaces and abstract classes — callers depend on the abstraction, not on the concrete implementation.

Interface-based abstraction

public interface PaymentProvider {
    PaymentResult charge(Money amount, Card card);
}

public class StripeProvider implements PaymentProvider { ... }
public class PaypalProvider implements PaymentProvider { ... }

public class CheckoutService {
    private final PaymentProvider provider;

    public CheckoutService(PaymentProvider provider) {
        this.provider = provider;
    }
}

CheckoutService knows nothing about Stripe or PayPal. Swap one for the other — no code changes in CheckoutService.

Abstraction vs encapsulation

Closely related but distinct. Encapsulation is about hiding internal state (implementation details of a single class). Abstraction is about exposing a simplified contract at a higher conceptual level (what operations are possible, regardless of implementation).

Layered abstractions

Modern codebases stack abstractions: Repository abstracts over a database; Service abstracts over business rules; Controller abstracts over HTTP plumbing. Each layer depends on the abstraction of the layer below, not the concrete implementation.

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