Hello everyone, I am Xiaomi! Today, I want to discuss in depth Pinduoduo’s interview question with you: What are the 7 ways to implement inheritance in Java? This is a rather in-depth question, but don't worry, I will try my best to explain it to you in an easy-to-understand way, so that everyone can have a deeper understanding of Java inheritance.
what is inheritance
In Java programming, inheritance is a very important concept that allows one class (subclass/derived class) to inherit the properties and methods of another class (parent class/base class). This mechanism helps code reuse and extension and is one of the cores of object-oriented programming (OOP). So, let's take a look at what are the ways to implement inheritance in Java!
Use the extends keyword
In Java, the most common way of inheritance is to use the extends keyword. In this way, a subclass can inherit the properties and methods of a parent class. For example:
Subclasses inherit the characteristics of the parent class and can override the methods of the parent class or add their own properties and methods.
Using interfaces to implement inheritance
Java also supports interface inheritance, which is a way to implement multiple inheritance. A class can implement multiple interfaces and thus obtain methods of multiple interfaces. For example:
By implementing an interface, a class can obtain the methods defined in the interface and must implement these methods.
Use abstract classes
An abstract class is a class that cannot be instantiated and is usually used as a base class for other classes. Subclasses need to inherit the abstract class and implement the abstract methods in it. For example:
Use inner classes
Inner classes are classes defined inside other classes and can access the properties and methods of the outer class. A special form of inheritance can be achieved through inner classes. For example:
Inner classes can access private members of outer classes, which is very useful in certain scenarios.
Use interface default methods
Java 8 introduced interface default methods, allowing to provide default implementations of methods in interfaces. This allows interfaces to also contain concrete methods, allowing the same implementation logic to be shared across multiple classes. For example:
Through the default method of the interface, the same method logic can be implemented in multiple classes.
Use annotations
Although annotations are typically used to mark classes and methods, they can also be used to implement a form of inheritance. By defining custom annotations and using them on a class, you can obtain metainformation about the class at runtime. For example:
Through custom annotations, you can add additional information to a class to achieve a special inheritance effect.
Using Lambda Expressions
Lambda expression is a functional programming method introduced in Java 8, which can be used to implement a single method in an interface (functional interface). Lambda expressions enable inheritance without creating a new class. For example:
Lambda expressions can be regarded as a lightweight inheritance method, used to implement methods of function interfaces.
END
In this article, we discussed seven ways to implement inheritance in Java, including using the extends keyword, interface implementation inheritance, abstract classes, inner classes, interface default methods, annotations, and Lambda expressions . Each method has its own unique uses and advantages, and it is important to choose the appropriate inheritance method based on the specific situation.
I hope this article can help you better understand the inheritance mechanism in Java and provide strong support for your Pinduoduo interview or Java learning. If you have any questions or suggestions, please leave a message in the comment area and Xiaomi will try its best to answer your questions. Thank you all for reading, see you next time!
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