Why learn GoF Design Patterns? Design patterns help you find out patterns in your code. It helps to visualize your code at a higher level and decompose it into logical units. What are Design Patterns? Design patterns are canonical solutions to recurring problems. They are different from a library that is called from your code. Neither are they framework which is a complicated collection of libraries. Frameworks typically calls your code. The 24 design patterns covered in GoF book can be divided into three categories. Creational Patterns . These patterns seek to answer - "How should objects be created?". Examples are - Factory, Abstract Factory, Singleton, Builder, Prototype, Dependency Injection. They usually seek to decouple the construction of an object from its use. There are advantages to doing this. Hide implementation of an object, only reveal its interface. Defer instantiation until run-time. Allow creation of finite number of instances. Have f...