java遺珠之協變返回型別
摘要：
版權宣告：本文為博主原創文章，未經博主允許不得轉載。https://blog.csdn.net/lastsweetop/article/details/82658312
子類重寫父類的方法時返回型別和父類方法的返回型別可以不同，但是子類的返回型別必須是父類方法返回型別的...
版權宣告：本文為博主原創文章，未經博主允許不得轉載。https://blog.csdn.net/lastsweetop/article/details/82658312
子類重寫父類的方法時返回型別和父類方法的返回型別可以不同，但是子類的返回型別必須是父類方法返回型別的子類。
父類
public class Bicycle {
private int cadence;
private int gear;
private int speed;
public Bicycle(int startCadence, int startSpeed, int startGear) {
gear = startGear;
cadence = startCadence;
speed = startSpeed;
}
public Bicycle newBike() {
return new Bicycle(1, 1, 1);
}
}
子類
public class MountainBike extends Bicycle {
public int seatHeight;
public MountainBike(int startHeight, int startCadence,
int startSpeed, int startGear) {
super(startCadence, startSpeed, startGear);
seatHeight = startHeight;
}
@Override
public MountainBike newBike() {
return new MountainBike(1, 1, 1, 1);
}
}
如果返回型別不是父類返回型別的子類就會報錯:attempting to use incompatible return type
@Override
public Object newBike() {
return new Object();
}