Java 为什么我的程序中只有三个对象中的一个运行？

我对java非常陌生，并试图掌握如何在彼此之间使用类。这是一个汽车银行贷款项目。我已经创建了Bil（Car）类的三个不同对象，当我通过方法bilLån（）运行这些对象时，它只运行行中的最后一个对象，在本例中是“Opel”-对象。它确实在运行，所以一定是逻辑错误

班克尔班

import java.util.Scanner;
import java.text.DecimalFormat;

public class bankLån {

    DecimalFormat df1 = new DecimalFormat("#.##");

    double price;
    int years;
    double interest;
    double interestDiv;;
    double oneYr = 14.99;
    double threeYr = 10.99;
    double fiveYr = 6.99;
    double tenYr = 2.99;
    double monthlyInterCalc;
    double monthlyPayment;
    double monthlyInterest;
    int months = 12;

    Scanner input = new Scanner(System.in);

    bankLån() {


    }

    public void carLoan() {

        System.out.println();

        System.out.println("You've picked: "+Car.carBrand+"!"); 
        price = (Car.carPrice) -  (Car.downPay);

        System.out.println("With a down payment of "+Car.downPay);

        System.out.println("It will cost you: "+price+"!");

        System.out.println("Our interests are: ");

        System.out.println("1 year = "+oneYr+"% \t 3 years = "+threeYr+"% \t 5 years = "+fiveYr+"% \t 10 years = "+tenYr+"%");

        do {    

            System.out.println("Please input amount of years: ");
            years = input.nextInt();

            if (years == 1) {

                interest = oneYr;

            }

            else if (years == 3) {

                interest = threeYr; 

            }

            else if (years == 5) {

                interest = fiveYr;  

            }

            else if (years == 10) {

                interest = tenYr;   

            }

            else    {

                System.out.println("That amount of years ain't available, please try again.");
            }


        }while(!(years == 1 || years == 3 || years == 5 || years == 10));

        interestDiv = interest / 100;

        monthlyInterCalc = (price / years) / (months);
        monthlyInterest = monthlyInterCalc * interestDiv;
        monthlyPayment = monthlyInterCalc + (monthlyInterCalc * interestDiv);


        System.out.println("Your interest will be: "+interest+"% and will cost you around: "+df1.format(monthlyInterest)+ " every month.");

        System.out.print("The monthly payment will be around: "+df1.format(monthlyPayment)+".");

        System.out.println();

    }



    public static void main(String[] args) {
        // TODO Auto-generated method stub

        Car ferrari = new Car("Ferrari","Red",1000000,50000);
        Car volvo = new Car("Volvo","White",170000,40000);
        Car opel = new Car("Opel","Blue",40000,10000);




        ferrari.carLoan();
        opel.carLoan();
        volvo.carLoan();

    }


}

班车

public class Car extends bankLån{

    static String carBrand;
    static String carColor;
    static double carPrice;
    static double downPay;

    Car(String brand, String color, double price, double downP) {

        carBrand = brand;
        carColor = color;
        carPrice = price;
        downPay = downP;


    }


}

在类Bil中，所有变量都是静态的。这意味着它们持有的值对于这个类的所有不同对象都是相同的。这会使您的对象法拉利和沃尔沃与欧宝具有相同的属性值，因为欧宝是在上一节中设置的

删除这些变量之前的static关键字

carLoan方法将Car作为静态类而不是对象进行访问

System.out.println("You've picked: "+Car.carBrand+"!"); 
    price = (Car.carPrice) -  (Car.downPay);

Car不是实例对象，它引用的是静态类，因此出现错误“无法静态引用非静态字段Bil.carBrand”

要解决此问题，请在方法中获取一个Car对象，并访问它而不是类

public void carLoan(Car car) {

    System.out.println();
    System.out.println("You've picked: "+car.carBrand+"!"); 
    price = (car.carPrice) -  (car.downPay);
    System.out.println("With a down payment of "+car.downPay);
    System.out.println("It will cost you: "+price+"!");
    System.out.println("Our interests are: ");
    System.out.println("1 year = "+oneYr+"% \t 3 years = "+threeYr+"% \t 5 years = "+fiveYr+"% \t 10 years = "+tenYr+"%");

    do {    
        System.out.println("Please input amount of years: ");
        years = input.nextInt();
        if (years == 1) {
            interest = oneYr;
        }
        else if (years == 3) {
            interest = threeYr; 
        }
        else if (years == 5) {
            interest = fiveYr;  
        }
        else if (years == 10) {
            interest = tenYr;   
        }
        else {
            System.out.println("That amount of years ain't available, please try again.");
        }

    }while(!(years == 1 || years == 3 || years == 5 || years == 10));

    interestDiv = interest / 100;
    monthlyInterCalc = (price / years) / (months);
    monthlyInterest = monthlyInterCalc * interestDiv;
    monthlyPayment = monthlyInterCalc + (monthlyInterCalc * interestDiv);

    System.out.println("Your interest will be: "+interest+"% and will cost you around: "+df1.format(monthlyInterest)+ " every month.");
    System.out.print("The monthly payment will be around: "+df1.format(monthlyPayment)+".");
    System.out.println();

}

---

@Farhan Qasim说您需要删除

静态

但若您想在每个对象中进行处理，则需要在方法
bilLån（）
中传递对象引用，如

public void bilLån(Bil  mBill) {

        System.out.println();

        System.out.println("You've picked: "+Bil.carBrand+"!"); 
        price = (mBill.carPrice) -  (mBill.downPay);

        System.out.println("With a down payment of "+mBill.downPay);

        System.out.println("It will cost you: "+price+"!");

        System.out.println("Our interests are: ");

        System.out.println("1 year = "+oneYr+"% \t 3 years = "+threeYr+"% \t 5 years = "+fiveYr+"% \t 10 years = "+tenYr+"%");

        do {    

            System.out.println("Please input amount of years: ");
            years = input.nextInt();

            if (years == 1) {

                interest = oneYr;

            }

            else if (years == 3) {

                interest = threeYr; 

            }

            else if (years == 5) {

                interest = fiveYr;  

            }

            else if (years == 10) {

                interest = tenYr;   

            }

            else    {

                System.out.println("That amount of years ain't available, please try again.");
            }


        }while(!(years == 1 || years == 3 || years == 5 || years == 10));

        interestDiv = interest / 100;

        monthlyInterCalc = (price / years) / (months);
        monthlyInterest = monthlyInterCalc * interestDiv;
        monthlyPayment = monthlyInterCalc + (monthlyInterCalc * interestDiv);


        System.out.println("Your interest will be: "+interest+"% and will cost you around: "+df1.format(monthlyInterest)+ " every month.");

        System.out.print("The monthly payment will be around: "+df1.format(monthlyPayment)+".");

        System.out.println();

    }

在主要方法中：

  public static void main(String[] args) {
        // TODO Auto-generated method stub

        Bil ferrari = new Bil("Ferrari","Red",1000000,50000);
        Bil volvo = new Bil("Volvo","White",170000,40000);
        Bil opel = new Bil("Opel","Blue",40000,10000);


        ferrari.bilLån(ferrari);
        opel.bilLån(volvo);
        volvo.bilLån(opel);

    }

您的所有字段都是静态的，这意味着它们存在于每个类中，而不是每个实例中。删除
static
限定符。
Bil
扩展
bankLån
的事实很奇怪。汽车是银行贷款吗？我们之间有“是”的关系吗？我能建议您只使用一种语言：
Bil
，
Lån
是丹麦语还是挪威语（对不起，不知道是哪种语言）
carBrand
，
carColor
等均为英语。坚持使用其中一个。嘿，安迪！很抱歉，现在除了“main”类的名称之外，所有内容都是英文的。我听到了，我一直在尝试删除它们，但是对象的值出现了错误，“bil.carBrand”，例如在方法中，“不能静态引用非静态字段bil.carBrand”。这是我首先将其更改为static的唯一原因。@JimNotCarry我不确定您是如何访问carLoan（）方法的，因为它是Main类中的一个方法，而不是Car类。将该方法移动到car类，使用该方法而不是使用变量car。
  public static void main(String[] args) {
        // TODO Auto-generated method stub

        Bil ferrari = new Bil("Ferrari","Red",1000000,50000);
        Bil volvo = new Bil("Volvo","White",170000,40000);
        Bil opel = new Bil("Opel","Blue",40000,10000);


        ferrari.bilLån(ferrari);
        opel.bilLån(volvo);
        volvo.bilLån(opel);

    }