Can abstract classes inherit entity classes?

The answer is ：yes！

give an example ：java in object Is an entity class , Other classes, including abstract classes, mostly inherit object.

But there is a precondition that the entity class must have an explicit constructor .

What is an explicit constructor ？

First of all, understand java Inheritance ： Subclasses inherit all but not the parent class constructs , A subclass can only call a parent class construct .

My personal understanding of explicit constructors is : Constructs that can be called by subclasses （ A subclass invokes a parent class construct as a prerequisite for inheritance ）, There are mainly the following 3 spot .

① The parent class writes a parameterless construct , Or don't write （ If you do not write, a parameterless structure will be generated by default ） Will be called by subclasses . Subclass not write construct , By default, a parameterless construct is generated and the first sentence is declared super（）; Subclasses that write constructs need to be declared in the construct super（）;

② The parent class writes a parameterized construct , Subclasses must have constructs and the first line of the construct declares super（） And the reference ;

③ By final Modifications cannot be inherited by subclasses , By private Modifiers are not visible to subclasses , Such inheritance cannot be implemented when it cannot be called and constructed by subclasses .

therefore , The premise of inheritance is that the parent class has a construct that can be called by its children . It doesn't really matter whether it is abstract or not , The entity class inherits the abstract class and also needs a parent class construct that can be called by itself .