Question

我正在尝试获取子类方法以从超类返回变量，但返回值不断给我空返回。我的猜测是我错过了对超类的某种引用。它是从子类方法returnweight（）返回值0（零）的值权重。

 abstract class Vehicle{
    protected float weight;
    public Vehicle(float weight){
    }
    public abstract float returnweight();
}

class Bike extends Vehicle{

    public Bike(float weight){
        super(weight);
    }
    public float returnweight(){
        return weight;//This returns as zero no matter what
    }
}

代码被压缩和翻译（在本文中不是编译器检查的语法）提前谢谢！

Answer 1

你有：

public Fordon(float weight) {  // What is Fordon? May be Vehicle is needed?
    // No code here?
    this.weight = weight; // Forgot this?
}

编辑：

public Vehicle(float weight) {
    // No code here?
    this.weight = weight; // Forgot this?
}

Answer 2

您的问题出在您的车辆超类中，构造函数没有做任何事情。

应该是：

public Vehicle(float weight){
   this.weight = weight;
}

这将允许您的自行车类（以及任何其他扩展Vehicle的类）通过调用超类的构造函数来实质设置权重;

Answer 3

提示：您确实正在返回已分配给weight的唯一值，但是，确实，赋值是隐式的。也许你的意思是在某些时候明确地为它指定一些其他值？也许在施工期间？

Java子类方法返回零值

3 个答案: