Pros of Dagger (Google)

• Supports Android development natively, with built-in Android modules
• Offers compile-time dependency injection, improving performance
• Provides better integration with other Google libraries and frameworks

Cons of Dagger (Google)

• Steeper learning curve due to more complex annotation processing
• Requires more boilerplate code for setup and configuration
• Less flexibility in certain scenarios compared to Square's version

Code Comparison

Dagger (Square):

@Inject
public MyClass(Dependency dependency) {
    // Constructor injection
}

Dagger (Google):

@Module
public class MyModule {
    @Provides
    public Dependency provideDependency() {
        return new Dependency();
    }
}

@Component(modules = MyModule.class)
public interface MyComponent {
    MyClass getMyClass();
}

Both Dagger implementations aim to provide dependency injection for Java and Android applications. While Square's version focuses on simplicity and ease of use, Google's version offers more advanced features and better integration with Android development. The choice between the two depends on project requirements, team expertise, and the specific ecosystem in which the application is being developed.

Pros of Guice

• More flexible and customizable, allowing for complex dependency injection scenarios
• Supports method and constructor injection, offering greater versatility
• Has a larger ecosystem and community support due to its longer existence

Cons of Guice

• Steeper learning curve and more complex setup compared to Dagger
• Runtime dependency resolution, which can lead to performance overhead
• Requires more boilerplate code for configuration

Code Comparison

Guice:

public class GuiceExample {
    @Inject
    private Service service;

    @Inject
    public GuiceExample(AnotherService anotherService) {
        // Constructor injection
    }
}

Dagger:

@Component(modules = AppModule.class)
public interface AppComponent {
    Service getService();
    AnotherService getAnotherService();
}

@Module
public class AppModule {
    @Provides
    static Service provideService() {
        return new ServiceImpl();
    }
}

Guice uses annotations for both field and constructor injection, while Dagger relies on components and modules for dependency configuration. Dagger's approach results in more compile-time safety and easier-to-read dependency graphs, but Guice offers more flexibility in how dependencies are injected and configured.

Pros of Koin

• Lightweight and easy to set up, with minimal boilerplate code
• Pure Kotlin DSL, making it more intuitive for Kotlin developers
• Simpler learning curve, especially for smaller projects

Cons of Koin

• Less compile-time safety compared to Dagger
• May not scale as well for large, complex projects
• Limited support for Java projects

Code Comparison

Koin:

val myModule = module {
    single { MyRepository() }
    factory { MyViewModel(get()) }
}

Dagger:

@Module
class MyModule {
    @Provides
    fun provideRepository(): MyRepository = MyRepository()

    @Provides
    fun provideViewModel(repo: MyRepository): MyViewModel = MyViewModel(repo)
}

Koin uses a more concise DSL for dependency declaration, while Dagger relies on annotations and generated code. Koin's approach is often simpler for small to medium-sized projects, but Dagger's compile-time checks can catch errors earlier in large, complex applications.

Both frameworks aim to solve dependency injection in Android and Kotlin projects, but they differ in their implementation and target use cases. Koin is often preferred for its simplicity and Kotlin-first approach, while Dagger is chosen for its robustness and performance in larger projects.

Pros of Toothpick

• Simpler API and easier learning curve for beginners
• Faster compile times due to less annotation processing
• More flexible scoping system with on-the-fly scope creation

Cons of Toothpick

• Less mature ecosystem and community support
• Fewer advanced features for complex dependency graphs
• Limited documentation compared to Dagger

Code Comparison

Toothpick:

@Inject
public MyClass(Dependency1 dep1, Dependency2 dep2) {
    // Constructor injection
}

Toothpick.openScope(AppScope.class).inject(this);

Dagger:

@Inject
public MyClass(Dependency1 dep1, Dependency2 dep2) {
    // Constructor injection
}

@Component(modules = AppModule.class)
public interface AppComponent {
    void inject(MyClass myClass);
}

DaggerAppComponent.create().inject(this);

Both libraries use similar annotation-based dependency injection, but Toothpick's setup is generally simpler. Dagger requires more boilerplate code for component creation and module configuration, while Toothpick uses a more straightforward scoping system. However, Dagger's additional complexity allows for more fine-grained control over the dependency graph, which can be beneficial in larger projects.