Overview of famous inner classes and anonymous inner classes

Inner class

Inner class ： A class defined in an external class is called an internal class
Inner class ：（ classification ）
1. Name the inner class
2. Anonymous inner class
3. Static inner class
4. Non static inner class

Name the inner class

Concept ： A class with a name is called a named inner class .
namely ：

Anonymous inner class

Concept ： Classes that are not named at the beginning are called anonymous inner classes .
Because you need a class name to create an object , But anonymous classes are born without class names , So when anonymous inner class is defined, it is defined together with the created object .

grammar ：

new  Parent constructor ([ parameter list ])| Interface (){    
	// Anonymous inner class body 
} 

for example ：

Object object = new Object() {
};

characteristic ：

1、 Anonymous inner classes are General class Of Subclass
2、 Anonymous inner classes are abstract class Of Subclass
3、 Anonymous inner classes are Interface Of Implementation class

example 、

public  class Mammal {
	public  void move () {		
	}
	public  void breath() {
	
	}
	public static void main(String [] args) {
		Mammal r =new Mammal() {						
			@Override
			public void breath() {
			System.out.println("awesuft");
			}						
			@Override
			public void move () {
				System.out.println("afky");
			}
		};
		r.move();
		r.breath();
	}
}

Hold down Ctrl key , Click with the mouse r.move(); Of move. We can enter Mammal Of move In the method .
namely ：r.move(); It's polymorphism .

Mammal r =new Mammal(){
}

This is an object of transformation . We can know new Mammal(){
} This is an anonymous inner class .Mammal Is his parent class name , And the definition of r yes Mammal class , So he is the object of transformation .

That is, it is proved that the anonymous inner class is a subclass of the ordinary class .

The same is true 2 and 3.

reflection ：

An anonymous inner class cannot be an abstract class , Anonymous classes have no names , If it can be an abstract class , Then the anonymous class must have subclasses , But because there is no name , So there are no subclasses

summary ：

Whether it's an anonymous inner class or a named inner class ,javac Will produce an independent class file ： After the compilation, the inner class will be compiled to be independent .class file ,

If the inner class is Name the inner class , Then the bytecode file name of the inner class is the class name of the outer class +$+ Inner class class name ;

If Anonymous inner class , Then the anonymous inner class bytecode file name is the outer class class name +$+ Numbers ;
If you define an inner class directly in a class , It is used in a similar way to the member variable ：

attach ：

1、 External classes or external interfaces public default ; But the inner class defined directly in the class , There can be public ~private
In the method / You cannot add an access modifier to a code block .

private Decorated member variables can be used in inner classes

2、 If you use the value of a local variable in an inner class , be ：JDK8.0 And above versions can be dispensed with final modification ,8.0 You have to use fianl

• Anonymous inner class No can Custom construction method , Because he doesn't have a class name ,
  But you can initialize member variables through non static code blocks ;
• Anonymous inner class No can Lower transformation , Because he doesn't have a class name

4. Anonymous inner classes can be defined in class , Method , Code block in .

5. You can add new properties and methods to anonymous inner classes , But these properties and methods cannot be called by the upper transformation object , It can only be called by anonymous inner class objects created in the way of non transformation objects