Freshman summer internship Day5_ two

Catalog

1. Guide pack ：

 2.

3.

4.

5. Permission modifier ：

 6. Code block ：

 7. abstract class

 8. Interface

 9. How to divide inheritance tree and interface , The idea is crucial , Be concise and efficient

 10. New feature expansion ：

 11.jdk9

 12. Interface polymorphism ！

 13. Adapter ：

 14. Inner class

 （1） Member inner class

 （2） Static inner class

 （3） Local inner classes （ Similar to the properties of local variables , It can be used final Decoration is not available public modification ）

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1. Guide pack ：

 2.

Shortcut key ,shift+fn+f6 You can select the variable you click on and select all the places where this variable appears , Unified modification .

3.

alt+ enter , Automatic guiding package ;ctrl + shift + u Capitalize

4.

final:

 

enhance readability ：

5. Permission modifier ：

 

 6. Code block ：

（1） Local code block ： End the life cycle of local variables in advance , Recycle after use , It's not often used now

（2） Building blocks of code ： It's eliminated , inflexible

  So now it is generally improved to ：

 （3）

 

  Apply to data initialization ：

  Written in static It also prevents this method from being called repeatedly, resulting in new

 7. abstract class

 

  Abstract class constructor function ：

 

 8. Interface

（1） Different from abstract classes

 （2） Format ：

 

 （3） characteristic ：

 （4） Using memory analysis tools ： 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

 （5） Abstract methods with multiple interfaces with identical names , We can rewrite it once

 （6） Summary ：

 9. How to divide inheritance tree and interface , The idea is crucial , Be concise and efficient

 10. New feature expansion ：

 

 

  So if show Is static , Then implement the show It's not called rewriting , Just like the name

Can pass infer.show(),inferImpl.show() Respectively called

 11.jdk9

 

 12. Interface polymorphism ！

 13. Adapter ：

 InterAdapter As the transition is empty

interImpl Change the implementation class to inheritance interadapter, Then rewrite whichever method you need .

 14. Inner class

 （1） Member inner class

 

 

  Permissions are the same as above ,private< Default <protected<public

 

  If the inner class is private , If you need to get it , Or put private Changed , Or just like the figure below , Return by method ：

  In fact, the internal source code of the iterator also operates in this way ：

  Now consider duplicate names ：

If there is no duplicate name ：

   Obviously, what you get is what the arrow points to a 

  Otherwise, it needs to be like this ：（ Similar to inheritance , Only that super Changed ）

  Memory analysis , That's true ： Still from the stack , Pile up , Method area analysis

First, enter the red line , Then put outer,inner Class bytecode file is loaded first , among ,outer and Inner It's separate.

Look at the picture below ：（ The bytecode file is in Out In file ）

  This is the result of compilation , It's separate.

So these two chain New It's like this in the stacking area ：

 

Through memory tools, you can see , Local variables of internal classes ： There is such a pointer

 

summary ： 

 （2） Static inner class

 

  You want to use non static members of external classes inside static classes , It has to be

 

Pay attention to the picture above , Calling static methods with objects can be called , But we do not advocate , So it didn't give a hint .

Call... With the class name ： 

 

 （3） Local inner classes （ Similar to the properties of local variables , It can be used final Decoration is not available public modification ）

  usage ：