Detailed introduction to JAVA basic inheritance (inheritance)

Inheritance (inheritance) is a very important concept in Java OOP. This article mainly introduces inheritance (inheritance), the basics of JAVA. Friends who need it can refer to

Inheritance (inheritance) is a very important concept in Java OOP. Inheritance is based on reusing methods and fields of existing classes, and you can also add new methods and fields. Java uses the extends keyword to indicate the inheritance relationship (is-a). The inherited class is called the super class (superclass), the base class (base class), the parent class (parent class), and the new class is called the subclass (subclass) , derived class (derived class) or child class (child class).

1.class:The basic unit in a programming language. Encapsulates data and functions together.

2. The base class contains the characteristics and behaviors shared by all its derived classes.

3. You can create a base class to represent the core concepts of certain objects in the system, and derive other types from the base class to represent the various ways in which this core can be implemented.

4. The private member derived class of the base class is inaccessible.

5. The exported class copies the interface of the parent class, so all messages that can be sent to the base class object can also be sent to the exported class object. The exported class has the same type as the base class.

6. Two methods can make the difference between the base class and the derived class:

1) Add new methods directly to the derived class;

2) Change the existing base class Behavior of class methods - overriding base class methods.

7.is-a and is-like-a:

1) is-a: The exported class and the base class have exactly the same interface, that is, the exported class and the base class are exactly the same type. For example: a circle is a geometric figure. To determine whether it is inheritance, you must determine whether is-a can be used to describe the relationship between classes and make it meaningful.

2) is-like-a: New interface elements are added to the exported type, that is, the interface is extended, and the base class cannot access the newly added methods. At this point the exported class is like a base class.

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