java中内部类是什么意思

public class Product1 {

class Design{

private String name = "P30 pro";

public String showName() {

return name;

}

}

class Content{

private int i;

Content(int value){

i = value;

}

int value() {return i;}

}

public void show(int value) {

Content c = new Content(value);

Design d = new Design();

System.out.println(d.showName());

System.out.println(c.value());

}

public static void main(String[] args) {

Product1 p = new Product1();

p.show(6000);

}

}