"Design pattern" Java design pattern the first lesson of the observer pattern

We can use a situation in our life to get to know the observer pattern.

In this age, it is possible that the old people in our family still keep the habit of reading newspapers every day. The newspaper is responsible for producing the content, organizing it into a newspaper, printing it every day, and then sending it to every user who has paid for the newspaper. So that the old man can look at what happens every day.

This is the most appropriate metaphor for the observer pattern. Subscribers and newspapers are a one-to-many relationship, every day as long as the content is updated, will be unified to send the newspaper to the user's hand, of course, if you do not want to subscribe, you can unsubscribe. The newspaper doesn't know your status and doesn't care if you read the newspaper. It is the duty to send the newspaper to your house on time and every day.

Here is a summary of some of the key points about the observer pattern when I read a book:

• Design principle: Strive for loose coupling between interacting objects.
• Defines a one-to-many dependency between objects, so that when an object changes, all its dependents are notified and updated automatically.
• The Observer pattern provides an object design that allows for loose coupling between the observer and the Observer.
• An observer is stateful.
• Observers can update the observer with a common interface
• Observers do not know the details of the observer, only that the observer implements the Observer interface
• The loosely coupled design allows us to build resilient OO systems that can cope with change because the interdependence between objects is minimized.
• Java has a built-in observer pattern, the observer interface and the observable class in the Java.util package, and you can use push and pull two ways
• Be aware of the limitations of the built-in observer pattern in Java, because Observer is a class, not an interface
• The MVC pattern is the best representation of the Observer pattern
• The observer pattern is also applied to the Javabeans,rmi.

"Design pattern" Java design pattern the first lesson of the observer pattern