[問題] 多型請教
class Building { }
public class Barn extends Building
{
public static void main(String[] args)
{
Building build1 = new Building();
Barn barn1 = new Barn();
Barn barn2 = (Barn) build1; //1
Object obj1 = (Object) build1; //2
String str1 = (String) build1; //3
Building build2 = (Building) barn1; //4
}
}
上面的程式，我知道 2 , 4 是對的，3是錯的。
書上寫1也是對的，可是這樣 父類別實體轉成子類別 有符合多型的精神嗎?
總覺得1怪怪的，能開導我一下嗎XD
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