Reusable solution to a commonly occurring problem within a given context in software design.
It is not a finished design that can be transformed directly into source or machine code.
Rather, it is a description or template for how to solve a problem that can be used in many different situations.
Design patterns are formalized best practices that the programmer can use to solve common problems when designing an application or system.
A design pattern that deals with creating object in a manner suitable to a situation
| Design pattern | Description |
|---|---|
| Factory | creating objects without having to specify the exact class of the object that will be created |
| Builder | constructing complex objects in a simplified manner |
| Singleton | restricting the instantiation of a class to one "single" instance |
A design pattern that deals with assembling objects and classes into a flexible and efficient structure
| Design pattern | Description |
|---|---|
| Adapter | allowing objects with incompatible interfaces to collaborate |
| Composite | composing objects into tree structures |
| Decorator | attaching new behaviors to objects |
| Facade | simplifying and restricting the code by a new wrapper class "facade" |
A design pattern that deals with communications between objects
| Design pattern | Description |
|---|---|
| Command | encapsulating in an object all data required to perform an action |
| Observer | notifying observers about changes in its state |
| Strategy | selecting an algorithm at runtime |