Question

我想创建我的对象car的实例。我的问题是我可以创建汽车对象的实例，例如Car car1 = new car（“ Audi”，“ A4”，“ BF10YMR”）;但是我想通过助手类来创建汽车对象。我该如何在main中将该助手类称为car类而不是carHelper类？

汽车对象需要创建一个随机的注册号，并且该注册号是在carHelper类中创建的。返回对象。

public class Car implements Comparable<Car>
{
   public class Car
   {
    private String make;
    private String model;
    private String registration;  

   public Car(String make, String model, String reg)
   {
   this.make= make;
   this.model= model;
   registration = reg;
   }
}

public class carHelper
{
  public car genCar()
  {
    String reg =   //some method to generate random registration.
    String Make =  //some method to randomly pick make from a list
    String model = //some method to randomly pick model from a list
    return new Car(make,model,registration);
   }
 } 

public class Garage
{
   public static void main (String args[])
   {
    Garage MyGarage = new Garage(); 
    Car car1 = new Car("Audi","A4","BF10YMR") //works, but doesn't use helper                                                                       
    Car car2 = carHelper.genCar();   // something like this?

    carHelper c = new carHelper();   // thought something like this but
    System.out.println(c.genCar());  // creates object of type carHelper 
                                     // not car.

   MyGarage.add(car1); 
   MyGarage.add(car2);   // gives me carHelper cannot be converted to Car

   }
}

public class GarageOp implements CarList
{
  public GarageOp()
  {
   list = new ArrayList<Car>(); 
  }

public boolean add(Car car) 
{
  if (list.contains(car) == false)
  {
     list.add(car); 
     return true;
  }
}

}

预期结果是使用helper类创建汽车对象，并将其添加到ArrayList中。

Answer 1

您可以在CarHelper中创建此列表，然后随机选择值并使用它们创建新的Car。 UUID会创建一个随机的128位（包括十六进制）数字并转换为字符串

public class CarHelper {

    private List<String> makeList = Arrays.asList("s", "t", "f", "n");
    private List<String> modelList = Arrays.asList("yyt", "32g", "dc3", "aas");

    public Car genCar() {
        String reg = UUID.randomUUID().toString();
        String make = makeList.get(new Random().nextInt(makeList.size() - 1));
        String model = modelList.get(new Random().nextInt(modelList.size() - 1));
        return new Car(make,model,reg);
    }
}

Answer 2

在CarHelper类中使genCar（）方法为Static。

public car static genCar(){
    // do stuff to create object
}

非静态方法可以访问静态变量或在Java中调用静态方法。

使用助手类实例化对象

2 个答案: