What are the advantages and disadvantages of using a constructor when implementing dependencies in code?

Advantages of constructor-based dependency injection:

• Explicit declaration of dependencies — all necessary objects are passed through constructor parameters, improving readability and testability.
• Ensuring immutability — dependencies can be made final, increasing reliability.
• Simplifying testing — mock objects can be easily substituted during unit tests.

Disadvantages:

• With a large number of dependencies, the constructor can become cumbersome.
• Not always convenient if dependencies are optional or need to be created lazily.

Example:

public class Service {
    private final Repository repository;

    public Service(Repository repository) {
        this.repository = repository;
    }

    public void doWork() {
        repository.saveData();
    }
}

Thus, the constructor provides explicit and reliable dependency injection, which promotes clean architecture.