extends inheritance

Inheritance is a prerequisite for polymorphic, if not inherited no polymorphism.

* Extraction is the common inheritance

Parent (base class, super tired) subclass (derived class)

Features: subclass can have a parent class "content" subclasses can have their own "content"

Regular access member methods

1 to create an object is first with whoever who, without looking up

The method returns the value 2 subclasses of the parent class must be less than equal to the return value of the parent

Object is the parent of all classes

3 subclass method permissions must be greater than or equal superclass method permissions

public>protected>(default)留空>private

Inheritance in the constructor

Constructor sub-class which has a default implicit "super ()" call. They must first implementation of the parent class constructor

2 subclass must call the parent class method with the super keyword

3super when you call must be the first statement, the subclass constructor does not call super times

4 subclasses access to the parent object super. Object Name

Subclasses access inherited methods super. The name of the parent class method

Subclasses access Super parent constructor ();

super and this can not be used

Abstract method

Uncertainty in the parent class implemented method body

Abstract methods must be written in an abstract class

public abstract class

public class abstract01 extends abstract1{
    @Override
    public void eat() {
        
    }
}