See Introduction to design patterns for an overview of the four types of design pattern. When it was first introduced, the Command pattern was sometimes explained as callbacks for Java .

The Observable design pattern is used in many important Java APIs. One well-known example is a JButton that uses the ActionListener API to execute an action. In this example, we have an ...

The event sourcing design pattern is particularly well-suited to temporal applications. A temporal application is one in which the state of the application evolves over time toward a given outcome.