静态内部类

public class JavaOne{
    public static void main(String[] args){
        Outer.Inner.fun();
        Outer.Inner in=new Outer.Inner();
        in.fun();
        Outer ou=new Outer();
        ou.f();
    }
}
class Outer{
    static int a=10;
    static class Inner{
        public static void fun(){
            System.out.println(a);
        }
    }
    public void f(){
        Inner i=new Inner();
        i.fun();
    }
}