Java 向上转型和向下转型

public Class Fruits{}public Class Apple extends Fruits{}public Class RedApple extends Fruits{}Apple apple = new Apple();//向上转-OKFruits fruits = (Fruits)apple;//向下转-Wrong,因为苹果不一定就是红苹果.RedApple redApple = (RedApple)apple;//-------------------------------分割线---------------RedApple redApple1 = new RedApple();//向上转-OK, 苹果是水果Fruits fruits = (Fruits)redApple1;//向下转-OK, 由于上面的水果之前是红苹果, 那么将水果强转为红苹果也就没有问题了.RedApple redApple2 = (RedApple)fruits;