test8.17

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因为Tricycle没有balance()函数，向下转型后Tricycle对象调用balance（）会报错

class Cycle

{Cycle(){System.out.println("Cycle constructor");}}
class Unicycle extends Cycle{
Unicycle(){System.out.println("Unicycle constructor");}
public void balance(){System.out.println("Unicycle.balance()");}
}
class Bicycle extends Cycle{
Bicycle(){System.out.println("Bicycle constructor");}
public void balance(){System.out.println("Bicycle.balance()");}
}
class Tricycle extends Cycle{
Tricycle(){System.out.println("Tricycle constructor");}
}
public class Test17 {
public static void main(String[] args) {
Cycle[] cycle={new Unicycle(),new Bicycle(),new Tricycle()};
for(Cycle c:cycle)
c.balance();
((Unicycle)cycle[0]).balance();
((Bicycle)cycle[0]).balance();
((Tricycle)cycle[0]).balance();
}
}

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