Question

一段JAVA程序代码求运行结果

import java.util.ArrayList;
class GrannySmith extends Apple {
public String toString() {
return "GrannySmith";
}
}
class Gala extends Apple {
public String toString() {
return "Gala";
}
}
class Fuji extendsApple {
public String toString() {
return "Fuji";
}
}
class Braeburn extends Apple {
public String toString() {
return "Braeburn";
}
}
public class GenericsAndUpcasting {
public static void main (String[] args) {
ArrayList<Apple>apples = newArrayList<Apple>();
apples.add(new GrannySmith());
apples.add(new Gala());
apples.add(new Fuji());
apples.add(new Braeburn());
for (Apple c: apples) {
System.out.println(c);
}
}
}
运行结果：？？？？

Answer 1

你给的程序有问题。缺少Apple类，ArrayList<Apple>apples = newArrayList<Apple>()里面new没有和ArrayList分开;

补全之后的运行结果：