The Mediator pattern is a behavioral pattern that defines an object that encapsulates how a set of objects interact with each other. It promotes loose coupling by keeping objects from referring to each other explicitly and allows for their interaction to be centralised in a mediator object. The main idea behind the Mediator pattern is to reduce the complexity of the interactions between objects by introducing a mediator object that handles the communication between them....

The Iterator pattern is a behavioral pattern that provides a way to access the elements of an aggregate object sequentially without exposing its underlying representation. The main idea behind the Iterator pattern is to provide a uniform interface for traversing different types of collections, such as arrays, lists, trees, and so on. This interface allows clients to iterate over the elements of a collection without having to know about the internal structure of the collection....

The Command pattern is a behavioral pattern that allows you to encapsulate a request as an object, thereby allowing you to parameterize clients with different requests, queue or log requests, and support undoable operations. The main idea behind the Command pattern is to separate the object that invokes the operation from the object that knows how to perform the operation. This separation allows you to decouple the client that sends the request from the receiver that performs the request, and also allows you to implement the request as an object that can be passed as a parameter, stored, or manipulated like any other object....

The Chain of Responsibility pattern is a behavioral pattern that allows you to create a chain of objects that can handle requests in a sequential order. Each object in the chain has the ability to handle the request, pass it on to the next object in the chain, or do both. The main idea behind the Chain of Responsibility pattern is to decouple the sender of the request from the receiver by creating a chain of objects, each of which has the ability to handle the request....

The Proxy pattern is a software design pattern that provides a surrogate or placeholder object to control access to another object. It is a structural pattern that allows you to create a class that represents the functionality of another class, while adding additional functionality such as access control, caching, or logging. The main idea behind the Proxy pattern is to provide a level of indirection between the client and the real object, allowing you to control access to the real object and add additional functionality without modifying the real object’s code....