Question

因此，对于这项任务，我必须创建一个汽车类（父级）和一个认证的公司（子级），我需要让父类有一种方法来检查它是否仍在保修期内。 * checkWarrantyStatus（）。该方法调用布尔值isCoveredUnderWarranty（）来验证汽车是否仍有保修。我的问题是在认证的自有类中我必须调用isCoveredUnderWarranty（）以查看它是否包含在延长保修期内，然后通过car方法中的checkWarrantyStatus（）调用它。我希望这是有道理的。总而言之，我需要在子课程中检查isCoveredUnderWarranty并提供延长保修信息。然后它必须移动到父类，因此可以通过checkWarrantyStatus调用它。这是我的代码，我有1个错误。

    public class Car {

    public int year;
    public String make;
    public String model;
    public int currentMiles;
    public int warrantyMiles;
    public int warrantyYears;
    int currentYear =java.util.Calendar.getInstance().get(java.util.Calendar.YEAR);

    /** construct car object with specific parameters*/
    public Car (int y, String m, String mod, int mi){
    this.year = y;
    this.make = m;
    this.model = mod;
    this.currentMiles = mi;
    }       


    public int getWarrantyMiles() {
    return warrantyMiles;
    }
    public void setWarrantyMiles(int warrantyMiles) {
    this.warrantyMiles = warrantyMiles;
    }
    public int getWarrantyYears() {
    return warrantyYears;
    }
    public void setWarrantyYears(int warrantyYears) {
    this.warrantyYears = warrantyYears;
    }

    public boolean isCoveredUnderWarranty(){
    if (currentMiles < warrantyMiles){
        if (currentYear < (year+ warrantyYears))
    return true;
    }
    return false;       
    }

    public void checkWarrantyStatus(){
    if (isCoveredUnderWarranty()){
    System.out.println("Your car " + year+ " " + make+ " "+ model+ " With "+        

    currentMiles +" is still covered under warranty");
    }
    else
    System.out.println("Your car " + year+ " " + make+ " "+ model+ " With "+ 

    currentMiles +" is out of warranty");

    }
        }

public class CertifiedPreOwnCar extends Car{



public CertifiedPreOwnCar(int y, String m, String mod, int mi) {
    super(mi, m, mod, y);


}
public int extendedWarrantyYears;
public int extendedWarrantyMiles;



public int getExtendedWarrantyYears() {
    return extendedWarrantyYears;
}
public void setExtendedWarrantyYears(int extendedWarrantyYears) {
    this.extendedWarrantyYears = extendedWarrantyYears;
}
public int getExtendedWarrantyMiles() {
    return extendedWarrantyMiles;
}
public void setExtendedWarrantyMiles(int extendedWarrantyMiles) {
    this.extendedWarrantyMiles = extendedWarrantyMiles;
}

public boolean isCoveredUnderWarranty() {
    if (currentMiles < extendedWarrantyMiles){
        if (currentYear < (year+ extendedWarrantyYears))
    return true;
    }
    return false;   
}
}
public class TestCar {


    public static void main(String[] args) {
        Car car1 = new Car(2014, "Honda", "Civic", 255);
        car1.setWarrantyMiles(60000);
        car1.setWarrantyYears(5);
        car1.checkWarrantyStatus();

        Car car2 = new Car(2000, "Ferrari", "F355", 8500);
        car2.setWarrantyMiles(20000);
        car2.setWarrantyYears(7);
        car2.checkWarrantyStatus();

        CertifiedPreOwnCar car3 = new CertifiedPreOwnCar(2000, "Honda", "Accord", 65000);   
        car3.setWarrantyYears(3);
        car3.setWarrantyMiles(30000);
        car3.setExtendedWarrantyMiles(100000);
        car3.setExtendedWarrantyYears(7);
        car3.checkWarrantyStatus();





    }           
}

Answer 1

在基类Car中，将数据成员设置为“private”。儿童无法访问其超级班的私人成员。考虑为您的数据成员使用“protected”或“public”，或者为Car类中的这些值提供getter（也包括受保护或公共）方法。

考虑以下示例：

class Parent {
  private int x;
  protected int y;
  public int z;
}

class Child extends Parent {
  public void doit(){ System.out.println(x); //compiler error }
  public void doit2(){ System.out.println(y); //allowed }
  public void doit3(){ System.out.println(z); //allowed }
}

编辑：

对于本帖子评论中所述的其他问题，目前CertifiedPreownCar的构造函数

public CertifiedPreOwnCar(int y, String m, String mod, int mi) {
  super(mi, m, mod, y);
}

我相信它应该是

public CertifiedPreOwnCar(int y, String m, String mod, int mi) {
  super(y, m, mod, mi);
}

使用您当前的变量名称很容易犯这个错误。虽然选择短变量名很有诱惑力，但它可能会引入简单的错误并使您的代码更难调试（特别是对于那些没有编写代码的人）。

考虑使用更具表现力的名称，例如'year'，'make'，'model'和'miles'

不确定我是否使用继承/多态问题？

1 个答案: