创建内容类的方式通过外部类的实例对象来创建
public class AA {
int a =1;
class BB {
int b=3 ;
}
public static void main(String[] args) {
AA a =new AA();
BB b=a.new BB();
System.out.println(a.a);
System.out.println(b.b);
}
}public class