Freshman summer internship Day5_ one

Catalog

  And output alignment

  Random numbers

static Or c++ equally , All class objects share

  Tool class ：

 static It's also the same as c++ equally ：

  Then explain from memory ：

Now let's re recognize main：

  Learn next Java Inheritance ：（ I'll fill in these details for half a day ）

 5.IDEA Debug memory and memory analysis tools ：

6. Member variables with duplicate names

 7. rewrite ：

 8.

 9.this,super summary

10. Shortcut key alt+insert Or download Ptg Plug-ins can simplify your hand typing process

11. polymorphic

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I learned a new thing earlier ：

  And output alignment

  Random numbers

  This is to not point to the same space ,new One came out

append Anything you add can be converted into characters

static Or c++ equally , All class objects share

 

 

  Tool class ：

Privatization is to prevent others from creating tool objects , Because it doesn't make sense . Generally defined as static class methods , Easy to use

 PS： This is the basic framework of a business

 static It's also the same as c++ equally ：

Because statics have little to do with objects , It is shared by objects of the same class , Of course not This.

  Then explain from memory ：

Static things load as the class loads , There is static content before there is no object .

Now let's re recognize main：

  Learn next Java Inheritance ：（ I'll fill in these details for half a day ）

Thought and c++ 10 Fen is the same , Except that multiple inheritance is not supported

  Here's a practical one , And what we often ignore in our daily study , But the actual development pays special attention to , That is, the subclass of the parent class should belong to a category , In line with the actual situation .

as well as , Another concept is called indirect parent  

  Subclasses can only access parent private

Add a label below

1.

 2.

 3.

  I'm mentioning , The object here is not used , Become garbage , The virtual machine will reclaim memory by itself

4.

 

Here the virtual method definition and c++ Dissimilarity ！

 5.IDEA Debug memory and memory analysis tools ：

First of all. ：

then Get the address in the terminal ：

  Then input jhsdb hsdb, get Jdk Built in memory analysis , Then click the first option below

  Then enter the process just obtained id

  See what you want to see next , But the specific representative data 、 Format , Need to check online slowly , It is another key point of study

jiu

  Address ： Black horse programmer Java Zero Basics Video Tutorial (2022 newest Java introduction , Including Stanford exercises + Force button algorithm problem + Big factory java Interview questions ）_ Bili, Bili _bilibili

 

  Quite powerful , But I can't fully understand it for the time being

6. Member variables with duplicate names

 7. rewrite ：

 

  matters needing attention ：

 5 and 6 essentially ：

 8.

 9.this,super summary

PS： Print out the structure of the object in memory ：

 

  From memory ：

  here this In the method show Is a local variable

  and this() This is the usage of

Because there must be a hidden or displayed one in other constructors of this class super 了 . Of course this() Must be on the first line

10. Shortcut key alt+insert Or download Ptg Plug-ins can simplify your hand typing process

11. polymorphic

 

 

 

 11. A technical ：

Judge a Is it right? dog type

 jdk12 New features in the future ：

 

Let's start like this