What are Java abstract classes and interfaces? A brief introduction to Java abstract classes and interfaces (examples)

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Recently, I learned the chapter about classes when studying Java programming language, and came into contact with abstract classes and interfaces. I personally have some understanding of abstract classes and interfaces, and I would like to share them with you here. Since this is my first time writing a blog, my understanding of the problem may also be deficient and narrow. I hope you can give me some advice. I also hope to learn and progress with you all

Abstract class:

My personal understanding of abstract class is: class is the result of abstraction of objective things, and abstract class is It is obtained by further abstracting the class. In other words, this is from a philosophical perspective. Philosophy will make a high degree of generalization and abstraction of things, and abstract classes also make a high degree of generalization and abstraction of related classes to extract their commonalities.

The following is the definition of abstract class and related examples.

　

Notes on abstract classes:

1. Abstract must be added when defining an abstract class, and the abstract class can contain abstract methods or ordinary methods. method.

2. Abstract methods cannot have a method body (for specific method content, please see the code above for details).

3. Abstract methods must be placed in abstract classes, and their specific implementation methods must be in subclasses.

4. Abstract classes cannot be implemented.

Interface:

The interface is modified by interface, which mainly defines the abstract methods that need to be implemented. Personally, I feel that the emergence of interfaces is mainly to solve the problem of limitations of abstract classes. As we all know, a class can only inherit one parent class, but a class can implement multiple interfaces, so you can use interfaces to let the class implement them. Let's look at an example below.

Notes:

1. The properties in the interface are all public static final modifications. If not written, they will default.

2. The methods in the interface are abstract methods and cannot have specific method content.

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