内部类和外部类的一个问题

Question

class Car
{
class Wheel
{
}
}

class PlaneWheel extends Car.Wheel
{
PlaneWheel(Car car)
{
car.super();//这里怎么理解？？
}
public static void main(String[] args)
{
Car car=new Car();
PlaneWheel pw=new PlaneWheel(car);
}
}

Answer 1

也许下面代码更有说服力：
[quote][code="java"]class Car {

public Car() {
    super();
}

void run() {

}

class Wheel {
    Wheel(){
        System.out.println("能否运行这里？");
    }
    void round() {
    }
}

}

public class PlaneWheel extends Car.Wheel {
PlaneWheel(Car car) {
car.super();// 这里怎么理解？？

}

public static void main(String[] args) {
    Car car = new Car();
    PlaneWheel pw = new PlaneWheel(car);
}

}[/code][/quote]