I. location

Defined under a class and modified by static

Two, structure

Static and non-static attributes and methods can be defined under static internal classes

3. Static Internal Classes Access External Classes

1. Non-static attributes and methods of external classes cannot be accessed

2. Calling attributes [methods]:

2.1 Write the attribute name directly [call method name]--- Essentially, it's the second.

2.1 External Class. Attribute Name [Method Name]

Source code:

class Outter {
     private static int b =3;
     
     public static void test(){
         System.out.println("External Class Static Method");
     }
     static class Inner{
        public void get(){
            System.out.println(b);//External static properties can be accessed
            test();//Access to external class static methods
        }
    }
}

Decompiled source code:

class Outter
{
    private static int b;
    
    public static void test() {
        System.out.println("\u5916\u90e8\u7c7b\u9759\u6001\u65b9\u6cd5");
    }
    
    static {
        Outter.b = 3;
    }
    
    static class Inner
    {
        public void get() {
            System.out.println(Outter.b);
            Outter.test();
        }
    }
}

IV. External Classes Access Static Internal Classes

class Outter {
     private static int b =3;
     
     public static void test(){
         System.out.println("External Class Static Method");
     }
     static class Inner{
         private int a = 1;
         
         private static int b = 2;
        
         public void get(){
            System.out.println("get");
        }
         
         public static void get2(){
             System.out.println("get2");
         }
        
    }
     
     public static void main(String[] args) {
        //Static variables-Method  --One way
        System.out.println(Inner.b);
        Inner.get2();
        //Static variables-Method  --Mode two
        System.out.println(Outter.Inner.b);
        Outter.Inner.get2();
        //Non static state--Mode 1
        System.out.println(new Inner().a);
        new Inner().get();
        //Non static state--Mode 2
        System.out.println(new Outter.Inner().a);
    }
}

Above is a summary of static internal classes, there are some wrong places, please give us more advice, and make progress together!!!