What is the difference between an abstract class and an interface?

Members of abstract classes can have access levels, while members of interfaces are all public levels.

Abstract classes can contain fields, while interfaces cannot, abstract classes can inherit interfaces, and interfaces cannot inherit abstract classes.

Members of abstract classes can have concrete implementations, while interfaces cannot.

Abstract subclasses can optionally implement abstract methods of their base classes, while subclasses of interfaces must implement.

1.There can be non-abstract methods in an abstract class, that is, there can be implemented methods (including constructors), and interface methods are all abstract methods.

2.Abstract classes can implement interfaces, but interfaces cannot inherit abstract classes (interfaces cannot inherit from any class, only interfaces).

3. Abstract classes can not implement all interface methods, and the rest of the methods can be left to subclasses. And a class that implements an interface must implement an interface so method.

Foolishness. Abstract classes are represented in the form of interfaces.

1. The meaning is different:

Interfaces (hardware class interfaces) refer to the communication rules between different functional layers of the same computer, which are called interfaces.

Abstract classes are used to represent abstract concepts derived from the analysis and design of problem domains, which are abstractions of a series of concrete concepts that look different but are essentially the same.

2. The existence of different situations:

There can be no non-abstract methods in the interface.

There can be non-abstract methods in an abstract class.

3. The member variables are different:

By default, the member variables in the interface are static constants.

Member variables in abstract classes can be modified by different modifiers.

4. The concept is different

An interface is a code of conduct.

An abstract class is an abstraction of an object.

1. Abstract classes can be instantiated directly, and using the new operator on abstract classes will result in compile-time errors. While some variables and values can be abstract at compile time, they must either be null or contain references to instances of non-abstract classes.

2. Abstract classes are allowed (but not required) to contain abstract members.

3. Abstract classes cannot be sealed.

The differences between abstract classes and interfaces are as follows:1. The common method provides the method body.

The interface can only contain abstract methods, static methods and default methods, and cannot provide method implementations for ordinary methods, while abstract classes can contain ordinary methods, and ordinary methods in the interface are abstract methods by default.

2. PublicStaticFinal.

The member variables in the abstract class can be of various types, while the member variables in the interface can only be of the publicstaticfinal type, and must be assigned, otherwise the compilation will not pass.

3. a constructor.

The interface is unbalanced and coarse can contain constructors, and abstract classes can contain constructors, and the constructors in abstract classes are not used to create objects, but are called by their subclasses to complete the initialization of abstract classes.

4. Initialize the block.

An interface cannot contain an initialization block, but an abstract class can contain an initialization block.

5. Inherit an abstract class and multiple interfaces.

A class can inherit only one abstract class, whereas a class can implement multiple interfaces.