Question

我试图为汽车经销商实施一个系统，但是当我尝试在派生类中实例化我的Car类时，我收到错误消息

Multiple markers at this line
- The constructor Car(String, int, String, String, double, double) is 
 undefined

这是父类Car：

package Number3;

public class Car {

private String plateNum;
private int year;
private String make;
private String model;
protected double costPrice;
protected double sellingPrice;

public Car()
{
    plateNum = "";
    year = 1990;
    make = "";
    model = "";
    costPrice = 0.0;
    sellingPrice = 0.0;
}

public Car(String plateNum,int year,String make,String model,double costPrice,double sellingPrice)
{
    this.plateNum = plateNum;
    this.year = year;
    this.make = make;
    this.model = model;
    this.costPrice = costPrice;
    this.sellingPrice = sellingPrice;
}

public double getCostPrice()
{
    return costPrice;
}

public double computeSellPrice()
{
    sellingPrice = costPrice;
    return sellingPrice;
}

public void displayCarDetails()
{
    System.out.println("Plate number: "+plateNum);
    System.out.println("Year: "+year);
    System.out.println("Make: "+make);
    System.out.println("Cost price: "+costPrice);
    System.out.println("Selling price: "+sellingPrice);
}

}

和子类newCar：

package Number3;

public class newCar extends Car{

private double tax;

public newCar(String plateNum,int year, String make, double costPrice, double sellingPrice, double tax)
{
    super(plateNum,year,make,costPrice,sellingPrice); //where the error is found
    this.tax = (25/100);
}

public double computeSellPrice()
{
    sellingPrice = costPrice + (costPrice * tax);
    return sellingPrice;
}

public void displayCarDetails()
{
    super.displayCarDetails();
}
}

任何帮助都将不胜感激。

Answer 1

Car构造函数的签名与派生类中的签名不匹配。

在Car课程中，这是构造函数：

public Car(String plateNum,int year,
      String make,String model,double costPrice,double sellingPrice) {
        ...
  }

是String, int, String, String, double, double)

在派生类中：

你有：

super(plateNum,year,make,costPrice,sellingPrice)

哪个是int, int, String, double, double

将Super类中的newCar调用中的参数更改为与Car类的构造函数匹配。也就是说，在newCar类中，行

super(plateNum,year,make,costPrice,sellingPrice)

应该是：

super(plateNum, year,
      make, model, costPrice, sellingPrice)

Answer 2

Car类没有带5个参数的构造函数。

定义为

public Car(String plateNum,int year,String make,String model,double costPrice,double sellingPrice)
{
 ...
}

并且您尝试在不传递model参数的情况下调用它。

super(plateNum,year,make,costPrice,sellingPrice); //where the error is found

Answer 3

你的超级/父类Car有一个无参构造函数public Car() {和以下6参数构造函数，它是使用关键字super从子/子类构造函数调用的

public Car(String plateNum,int year,String make,String model,double costPrice,double sellingPrice)

请注意，它期望String model作为其第四个参数，但是您的public newCar()构造函数只传递了五个参数。缺少参数model。

public newCar(String plateNum,int year, String make, double costPrice, double sellingPrice, double tax)
{
    super(plateNum,year,make,costPrice,sellingPrice); // model MISSING!

因此，要修复它，要么修改构造函数以接受model（就像在usedCar()构造函数中一样）或将null传递给超类构造函数

super(plateNum,year,make,null,costPrice,sellingPrice); // model = null

未定义的构造函数错误

3 个答案: