Design Pattern

1. Design Pattern

• Design Pattern is a repeatable-solution/ template for a commanly recurring problem in software design.
• The developement paradigms have been tested and proven, so by using it we could: 1) Speed up the development process. 2) Prevent subtle issues and improve coding readability.

2. Creational Patterns

• Creational Patterns are desin patterns that deal with object creation mechanisms, trying to create objects in a suitable manner under specific situation.

  2.1 Sigleton Pattern

• Singleton pattern ensures, one class only has one instance, and provides a global point of access to it.
• Examples

  // not thread safe
  class Singleton { 
      private static Singleton singleInstance = null; 
  
      private Singleton() {
      } 
  
      public static Singleton getInstance() { 
          if (singleInstance == null) {
              singleInstance = new Singleton(); 
          }
    
          return singleInstance; 
      } 
  } 
  
  // thread safe
  class Singleton{
      private static Singleton singleInstance = new Singleton();
  
      private Singleton() {
      }
  
      public static Singleton getInstance(){
          return singleInstance;
      }
  }

2.2 Factory Pattern

• Factory Pattern defines an interface for creating an object, but let subclasses decide which class to instantiate. Factory method pattern lets a class defer instantiation to subclasses.

3. Structural Patterns

4. Behavioral Patterns