可将子类对象放入保存父类对象的容器内。
package com.htxx.action.business;
import java.util.ArrayList;
import java.util.List;
public class Cycle {
void ride(Cycle c){
System.out.println("ride");
}
public static void main(String[] args) {
List<Cycle> list=new ArrayList<Cycle>();
list.add(new Unicycle());
list.add(new Bicycle());
list.add(new Tricycle());
for(Cycle c:list){
System.out.println(c.toString());
}
}
}
class Unicycle extends Cycle{
}
class Bicycle extends Cycle{
}
class Tricycle extends Cycle{
}