関連ワード:  why we create abstract class in java    why we use abstract class in java    why we use abstract class in java instead of interface    why we use abstract class in java with example    why do we use abstract class in java    why we use abstract class and interface in java    why we use interface over abstract class in java    why we can't create object of abstract class in java    why we use interface when we have abstract class in java    why we can't create object of abstract class and interface in java