Question

我是Java的新手，我无法解决这个问题。我尝试在我的对象的参数中传递值，但它只想转到没有参数的构造函数。另外2个有多个参数，但它没有注意到它？提前谢谢！

以下是代码：

    Car vehicle1 = new Car();
    Car vehicle2 = new Car();
    Car vehicle3 = new Car();

public Car() {

    private int numberOfCars;

    private String company;
    private String modelName;
    private String modelYear;
    private double hp;
    private int doors;
    private String gears;
    private String color;
    private boolean racingCar;
    private double price;

        numberOfCars = -1;
        company = "***EMPTY***";
        modelName = "***EMPTY***";
        modelYear = "***EMPTY***";
        hp = -1;
        doors = -1;
        gears = "***EMPTY***";
        color = "***EMPTY***";
        racingCar = false;
        price = -1;
    }
    public Car(String companyName, String modelNa, String modelYe){

        numberOfCars = -1;
        company = companyName;
        modelName = modelNa;
        modelYear = modelYe;
        hp = -1;
        doors = -1;
        gears = "***EMPTY***";
        color = "***EMPTY***";
        racingCar = false;
        price = -1;
    }
    public Car(int carAmount, String companyTitle, String modelTitle, String modelBirth, double horsePower, int door, String gearType, String colors, boolean raceCar, double prices){

        numberOfCars = carAmount;
        company = companyTitle;
        modelName = modelTitle;
        modelYear = modelBirth;
        hp = horsePower;
        doors = door;
        gears = gearType;
        color = colors;
        racingCar = raceCar;
        price = prices;
    }

Answer 1

为了调用其他构造函数，您需要在构建对象时指定参数：

Car vehicle1 = new Car();
Car vehicle2 = new Car("companyName", "modelNa", "modelYe");
Car vehicle3 = new Car(2, "companyTitle", "modelTitle", "modelBirth", 5.2, 4, "gearType", "colors", false, 1600);

Answer 2

这是您正面临的问题的完整编码

class Car
{
  String company;
  String modelName;
  String modelYear;
  double hp;
  int doors;
  String gears;
  String color;
  boolean racingCar;
  double price;
  int numberOfCars;



  public Car() {

    numberOfCars = 1;
    company = "BMW";
    modelName = "BMW M3 DTM";
    modelYear = "2012";
    hp = 500;
    doors = 2;
    gears = "Clutch";
    color = "Black";
    racingCar =true;
    price = -1;
   }

 public Car(String companyName, String modelNa, String modelYe){

    numberOfCars = 1;
    company = companyName;
    modelName = modelNa;
    modelYear = modelYe;
    hp = 500;
    doors = 2;
    gears = "Clutch";
    color = "White";
    racingCar = true;
    price = 100000;

}
public Car(int carAmount, String companyTitle, String modelTitle, String modelBirth, double horsePower, int door, String gearType, String colors, boolean raceCar, double prices){

    numberOfCars = carAmount;
    company = companyTitle;
    modelName = modelTitle;
    modelYear = modelBirth;
    hp = horsePower;
    doors = door;
    gears = gearType;
    color = colors;
    racingCar = raceCar;
    price = prices;

}

public static void main(String args[]) 
 {
Car vehicle1 = new Car();
Car vehicle2 = new Car("BMW", "BMW M3 DTM", "2012");
Car vehicle3 = new Car(1, "BMW", "BMW M3 DTM", "2012", 500, 2, "Clutch", "White", true, 5000000);
}
}

在使用构造函数之前，您应该了解一些基本事实

无参数 - 编译器将搜索没有参数的方法/构造函数
使用参数 - 编译器将使用您在调用时指定的参数搜索Method / Constructor。
同样类型＆amp; 数量参数

谷歌，你会发现理论！

Answer 3

像Guillaume所说，当您实例化对象时，需要使用参数调用参数化构造函数。你可以看到这个例子

http://beginnersbook.com/2014/01/parameterized-constructor-in-java-example/

Answer 4

通常，如果您编写一个类并且不包含任何构造函数，Java会自动为您提供一个默认构造函数（一个没有参数），并且虚拟机会初始化该类的所有实例变量（如果有的话）默认值（0，null或false）。但是，如果使用某些参数编写构造函数，并且不编写任何默认构造函数，则Java不提供默认构造函数。 see here 表示你在这里粘贴的代码可能会错过一个no-arg构造函数？

请注意，要使用参数调用构造函数，需要在实例化对象时提供参数。

调用多个构造函数 - 只进入同一个构造函数？

4 个答案: