Analyze the role of interfaces in Java

This article mainly introduces the role of Java interfaces and involves knowledge about the specifications of interfaces. Friends who need it can refer to it

1. The interface is a specification

Very good, you already know that interface is a specification!

The picture below shows the interface we encounter in our lives: the power socket interface.

#2. Why are specifications needed?

Because of the interface specification:

• Any electrical appliance can get power as long as it has a plug that meets the specification

• Any manufacturer (Siemens socket, TCL socket, Bull socket...) can provide power if it is made according to the specifications

The production technology and process of each manufacturer's socket are different, because the interface The implementation can be different, but it does not affect the normal operation of the appliance. The internal implementation of the socket is completely shielded from the appliance.

The same is true for software development:

• By calling methods according to the interface specification, you can obtain the desired functions

• Implementing the method of the interface according to the interface specification , can provide the desired functions

The next is the key point:

• Software development is mostly a collaborative work: electrical appliances and sockets are created by different people Once completed, with the interface, everyone can work separately and work according to the interface. After each work is completed, they can be easily integrated together. Testing of various parts is also more convenient.

• Software needs to continue to evolve: today you use a Bull socket, and a year later you may change to a Siemens socket. If you don’t have this set of national interface standards and do your own thing, then you probably won’t be able to change the socket. . Think about it, every time we go to the United States for a business trip, we have to bring an adapter, otherwise we will be on our knees. How inconvenient it is because the interface specifications are different! (Do you smell a strong Adapter mode smell from these adapters?)

3. When do you need to establish specifications through interfaces

In order to abstract some public behavior of the system, or encapsulate variability, you need to extract it when designing the system interface so that your system will be more flexible in the future. As you said, the method of directly writing the implementation is of course also possible in deterministic scenarios. When factors such as division of labor and collaboration, variability, and test convenience are not involved, of course there is no need for interfaces. For example, under normal circumstances, you don't need to separate the interface and implementation for a Pojo's getter and setter. Therefore, the object-oriented masters tirelessly teach us: separate interface and implementation, and interface-oriented programming.

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