A.多態(tài)創(chuàng)建的對象只能調(diào)用到父類聲明過的方法
B.兩個不相關(guān)的類，對象類型能相互轉(zhuǎn)換
C.向下轉(zhuǎn)型都能成功
D.向上轉(zhuǎn)型需要類型的強制轉(zhuǎn)換

A.public class SubClass SuperClass{}
B.public class SubClass extends SuperClass{}
C.public class SubClass static SuperClass{}
D.public class SubClass void SuperClass{}