The foremost design pattern in Android development is crucial for developers to master.

What Does Design Pattern Mean?

Design patterns are reusable solutions to common software engineering challenges. Unlike custom solutions for specific programs, they’re versatile templates applicable across various contexts and subject to refinement. They help speed up development by leveraging proven prototypes, leading to more efficient coding and readable final products.

Singleton Pattern:

The Singleton Pattern is a design concept where only one instance of a class can be created, and access to that instance is provided. It involves static variables that store unique and private instances. This pattern is useful when you want to restrict the creation of a class to a single object, especially handy for coordinating actions across a system.

Creational Patterns

Properties of Singleton Class

  1. Only one instance
  2. Globally accessible

Rules for making a class Singleton

The following rules are followed to make a Singleton class:

  1. A private constructor
  2. A static reference of its class
  3. One static method
  4. Globally accessible object reference
  5. Consistency across multiple threads

Singleton Example:

Following is the example of Singleton class in java:
Following is the example of Singleton class in Kotlin:

Factory Pattern:

As the name suggests, Factory takes care of all the object creational logic. In this pattern, a factory class controls which object to instantiate. Factory pattern comes in handy when dealing with many common objects. You can use it where you might not want to specify a concrete class.

Take a look at the code below for a better understanding:

Builder Pattern:

Builder pattern aims to “Separate the construction of a complex object from its representation so that the same construction process can create different representations.” It is used to construct a complex object step by step and the final step will return the object.

Creational Patterns

Rules for making a Builder class

The following rules are followed to make a Builder class:

  1. A private constructor
  2. An inner class usually called Builder
  3. function for each field to set the field value return
  4. function build return instance of the Main class
Following is the example of Builder class in Kotlin:

Facade Pattern:

The Facade pattern provides a higher-level interface that makes a set of other interfaces easier to use. The following diagram illustrates this idea in more.

Square’s Retrofit is an open-source Android library that helps you implement the Facade pattern. You create an interface to provide API data to client.