Abstract encapsulation inheritance polymorphism

Catalog

Inherit

super Be careful :

rewrite

polymorphic

instanceof

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Inherit

Inheritance is extension A subclass is an extension of the parent class

Inheritance only supports single inheritance

As long as the subclass inherits the parent class Have all the methods of the parent class

super Be careful :

1. super  Call the constructor of the parent class , Must be in the first... Of the construction method
super Must only appear in a subclass's method or constructor !
3. super and  this  Cannot call constructor at the same time !
 this:
Different objects represented :
this: Calling the object itself
super:
Represents the application of the parent object
Premise
this: You can use without inheritance
super: Can only be used in inheritance conditions
Construction method
this() ： The construction of this class
super(): Construction of parent class !

rewrite

： It has nothing to do with attributes It's all about rewriting methods

Rewrite should have inheritance relationship Subclass override parent method

1 Same method name

2 Same parameter list

3 The range of modifiers can be expanded But you can't shrink

polymorphic

One A The type handle can point to the address of the object of its own class , It can also point to the address of any descendant class object

instanceof