関連ワード:  why do we use abstract class in java    why do we need abstract class in java    why do we use interface instead of abstract class in java    why do we need interface and abstract class in java    why we use abstract class in java with example    why do we create abstract class in java    why we need abstract class in java 8    why do we need interface when we have abstract class in java    why we use interface over abstract class in java    where we can use abstract class in java