Design Patterns

Chain of responsibility

Filtering access shows how a request containing user data passes a sequential chain of handlers that perform various things such as authentication, authorization, and validation. From: https://refactoring.guru/design-patterns/chain-of-responsibility/java/example

Command

Text file implement all functionality required for performing some text-file related operations, such as opening, writing, saving a text file, and so forth. From: https://www.baeldung.com/java-command-pattern

Observer

Text editor example each time the Editor object changes, it notifies its subscribers. EmailNotificationListener and LogOpenListener react to these notifications by executing their primary behaviors. From: https://refactoring.guru/design-patterns/observer/java/example

State

Package which is sent to a post office, the package itself can be ordered, then delivered to a post office and finally received by a client. Now, depending on the actual state, we want to print its delivery status. From: https://www.baeldung.com/java-state-design-pattern

Strategy

Payment methods is used to implement the various payment methods in an e-commerce application. After selecting a product to purchase, a customer picks a payment method: either Paypal or credit card. From: https://refactoring.guru/design-patterns/strategy/java/example

Visitor

Exporting shapes into XML export a set of geometric shapes into XML. The catch is that we don’t want to change the code of shapes directly or at least keep it to the minimum. From: https://refactoring.guru/design-patterns/visitor/java/example

Template Method

Template Method pattern defines an algorithm of working with a social network. Subclasses that match a particular social network, implement these steps according to the API provided by the social network. From: https://refactoring.guru/design-patterns/template-method/java/example

Mediator

Imagine we're building a simple cooling system that consists of a fan, a power supply, and a button. Pressing the button will either turn on or turn off the fan. Before we turn the fan on, we need to turn on the power. Similarly, we have to turn off the power right after the fan is turned off. From: https://www.baeldung.com/java-mediator-pattern

Interpreter

Create a simple SQL-like syntax in an object-oriented way, which will be then interpreted and return us the result. From: https://www.baeldung.com/java-interpreter-pattern