Is an interface in java a special abstract class?

The interface in Java is a special abstract class. All methods in the interface are abstract methods, and all attributes in the interface are constants; that is, there are only method definitions in the interface but no methods. accomplish. Interfaces are a means to solve the problem that Java cannot use multiple inheritance, but in practice, interfaces play more of a role in setting standards.

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Java interface is a declaration of a series of methods. It is a collection of method characteristics. An interface only has method characteristics but no method implementation. Therefore, these methods can be implemented by different classes in different places, and these implementations can have different behaviors (functions). An interface can be understood as a special class, which is composed of global constants and public abstract methods. Interfaces are a means to solve the problem that Java cannot use multiple inheritance, but in practice, interfaces play more of a role in setting standards. Or we can directly understand the interface as a 100% abstract class, that is, all methods in the interface must be abstract methods.

What is the interface used for?

By using the interface, the same behavior of related classes can be achieved without considering the hierarchical relationship between these classes. The interface is the implementation class External appearance.

The idea of ​​interface

The idea of ​​interface is "encapsulation and isolation"

The benefits of using interfaces

Since external calls and internal implementation are separated by the interface, as long as the interface remains unchanged, changes in the internal implementation will not affect external applications, making the system more flexible, with better scalability and maintainability, which also It is the so-called "interface is the guarantee of system pluggability".

Selection of interfaces and abstract classes

Since the interface is a special abstract class, when should you choose an interface during development? When to choose abstract classes?

• Preferred interface

• When you want to define the behavior of a subclass and provide public functions for the subclass, you should choose an abstract class

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