Design Patterns Series – Introduction to Behavioral Patterns How Objects Communicate in a Clean and Maintainable Way
In the previous articles, we explored:
• Creational Patterns – How objects are created • Structural Patterns – How objects and classes are organized
Now let's move to the third category of design patterns:
Behavioral Design Patterns
Behavioral patterns focus on how objects interact and communicate with each other.
Instead of focusing on how objects are created or structured, these patterns solve problems related to:
• Communication between objects • Responsibility distribution • Flexible workflows • Reducing tight coupling between components
In simple terms:
Behavioral patterns help objects collaborate efficiently without knowing too much about each other.
This is extremely important in large-scale systems and Android applications, where components like ViewModels, Repositories, Services, and UI layers must communicate cleanly.
Why Behavioral Patterns Matter
As applications grow, direct communication between objects can create problems such as:
• Tight coupling • Hard-to-maintain logic • Complex conditional flows • Difficult testing
Behavioral patterns solve these issues by introducing structured communication mechanisms.
This results in:
✔ Better separation of concerns ✔ Easier testing ✔ More flexible system behavior ✔ Cleaner architecture
Types of Behavioral Design Patterns
There are 11 behavioral design patterns commonly used in software design.
Core Behavioral Patterns
1️⃣ Observer Pattern Used when an object needs to notify multiple dependents automatically.
Example: Android LiveData / Flow observers
2️⃣ Strategy Pattern Allows selecting an algorithm at runtime.
Example: Different payment strategies in an e-commerce app.
3️⃣ Command Pattern Encapsulates a request as an object.
Example: Undo/Redo functionality.
4️⃣ Iterator Pattern Provides a way to traverse elements without exposing internal structure.
Example: Kotlin collections iteration.
5️⃣ Mediator Pattern Centralizes communication between multiple objects.
Example: Chatroom system or event coordinators.
6️⃣ State Pattern Allows an object to change behavior based on its internal state.
Example: Order status: Pending → Processing → Delivered.
7️⃣ Template Method Pattern Defines the skeleton of an algorithm but allows subclasses to override steps.
8️⃣ Chain of Responsibility Passes requests through a chain of handlers.
Example: Request processing pipelines.
9️⃣ Visitor Pattern
Separates algorithms from object structures.
🔟 Memento Pattern
Captures and restores object state.
1️⃣1️⃣ Interpreter Pattern
Defines grammar for a language and interprets sentences.
Behavioral Patterns in Android Development
These patterns appear frequently in modern Android architecture.
Examples include:
Observer Pattern
Used in:
Strategy Pattern
Used in:
Command Pattern
Used in:
Example – Observer Pattern (Kotlin)
A simple example of a publisher-subscriber relationship.
interface Observer {
fun update(message: String)
}
class User(private val name: String) : Observer {
override fun update(message: String) {
println("$name received notification: $message")
}
}
class NotificationService {
private val observers = mutableListOf<Observer>()
fun subscribe(observer: Observer) {
observers.add(observer)
}
fun notifyUsers(message: String) {
observers.forEach { it.update(message) }
}
}
fun main() {
val service = NotificationService()
val user1 = User("Alex")
val user2 = User("Sam")
service.subscribe(user1)
service.subscribe(user2)
service.notifyUsers("New article published!")
}
This pattern allows multiple users to receive updates without tightly coupling them to the notification system.
When to Use Behavioral Patterns
You should consider behavioral patterns when:
• Objects need to communicate in complex ways • Responsibilities need to be distributed cleanly • System behavior must change dynamically • You want to reduce tight coupling
What’s Next in This Series?
In the next article, we will go deeper into the first Behavioral Pattern:
Observer Pattern – One-to-Many Object Communication
We will explore:
• Real-world examples • Kotlin implementation • Android architecture usage • When to use it and when to avoid it
Final Thoughts
Understanding behavioral patterns helps developers design systems where components collaborate smoothly while remaining loosely coupled.
This leads to:
• Cleaner code • Scalable architecture • Easier maintenance
And most importantly — better software design.
If you're learning System Design and Software Architecture, understanding these patterns is a huge step forward.
Follow along as we explore each pattern in detail.
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