使用Class的isAssignableFrom方法可是實現。但是注意不要弄反了！
public?class?AssignableFromTest?extends?TestCase?{
????class?A?{}
????class?B?extends?A{}
????
????public?void?testIt(){
????????A?a?=?new?A();
????????B?b?=?new?B();
????????assertTrue(a.getClass().isAssignableFrom(b.getClass()));
????}
}