JAVA数组与对象错误问题(初学者)

Question

我的任务是编写一个程序，根据以下三个因素来预测您的年度燃料使用量汽车加油。我必须使用两个单独的类。这是我的第一个类，名为 AnnualFuelUse。

public class AnnualFuelUse
{
private static int endMiles, startMiles,fillUp, days,distance;
private double gallonsUsed, pricePerGallon,MPG,cost;
//constructor
AnnualFuelUse(int fu, int days, int sm, int em, double gu, double price)
{
    fillUp = fu;
    days = days;
    startMiles = sm;
    endMiles = em;
    gallonsUsed = gu;
    pricePerGallon = price;
    distance = 0;
    MPG = 0.0;
    cost = 0.0;
}
//calculates distance
public void calcDistance ()
{
    distance = endMiles - startMiles;

}

public int getDistance(){
    return distance;
}

//calculates miles per gallon
public void calcMPG()
{
    MPG =  distance /gallonsUsed;
}
public double returnMPG(){
    return MPG;
}
//calculates total cost
public void totalCost(){
    cost= gallonsUsed * pricePerGallon;

}
public double getCost(){
    return cost;
}

这是我的第二堂课，名为 AnnualFuelUseTester。 (抱歉，名称太长，但这是必需的)

public class AnnualFuelUseTester
{
public static void main(String[]args)
{
    int fillUp1,fillUp2,fillUp3,days1,days2,days3,startMiles1,startMiles2,startMiles3;
    int endMiles1,endMiles2,endMiles3,distance1,distance2,distance3;
    double gallons1,gallons2,gallons3,MPG1,MPG2,MPG3,price1,price2,price3;
    double cost1,cost2,cost3;

    AnnualFuelUseTester[]fuel = {new AnnualFuelUseTester(1,1,45023,45231,10.00,2.95),
                                 new AnnualFuelUseTester(2,4,45231,45480,11.70,2.99),
                                 new AnnualFuelUseTester(3,8,45480,45659,9.30,3.01)};

    for (int index = 0; index<fuel.length;index++)
    {
        fuel[index].calcDistance();
        fuel[index].calcMPG();
        fuel[index].totalCost();
    }

    System.out.println(" Fill Up  Days   Start Miles   End Miles   Distance   Gallons Used   MPG   Price   Cost   ");;
    for(int index = 0; index < fuel.length; index++)
    {
        System.out.printf("%5i %5i %5i %5i %5i %5.2d %5.2d %5.2d %5.2d %n",
        fillUp,days,startMiles,endMiles,fuel[index].getDistance(),gallonsUsed,fuel[index].getMPG(),price,fuel[index].getCost());
    }


}
}

到目前为止，我遇到的问题是，当我运行它时，出现错误，指出 AnnualFuelUseTester in类 AnnualFuelUseTester 不能应用于给定类型；必需:无参数；发现: int,int,int,int,double,double;原因:实际参数列表和形式参数列表的长度不同。

我认为这说明了长度或类型不正确匹配，但据我所知，似乎没问题。我不确定如何解决这个问题，希望得到一些帮助。

即使我修复了这个问题，我也不知道代码是否会正确运行，但我现在无法再进一步，所以我尝试一次迈出一步。如果您发现任何明显的错误，请指出，以便我找出解决方法。

我将 AnnualFuelUseTester 编辑为:

public class AnnualFuelUseTester
{
public static void main(String[]args)
{
    int fillUp1 = 0 ,fillUp2 = 0,fillUp3 = 0,days1 = 0,days2= 0,days3= 0,startMiles1=     0,startMiles2= 0,startMiles3= 0;
    int endMiles1= 0,endMiles2= 0,endMiles3= 0,distance1= 0,distance2= 0,distance3= 0;
    double gallons1= 0,gallons2= 0,gallons3= 0,MPG1= 0,MPG2= 0,MPG3= 0,price1= 0,price2= 0,price3= 0;
    double cost1= 0,cost2= 0,cost3= 0;

    AnnualFuelUse[]fuel = {new AnnualFuelUse(1,1,45023,45231,10.00,2.95),
                           new AnnualFuelUse(2,4,45231,45480,11.70,2.99),
                           new AnnualFuelUse(3,8,45480,45659,9.30,3.01)};

    for (int index = 0; index<fuel.length;index++)
    {
        fuel[index].calcDistance();
        fuel[index].calcMPG();
        fuel[index].totalCost();
    }

    System.out.println(" Fill Up  Days   Start Miles   End Miles   Distance   Gallons Used   MPG   Price   Cost   ");;
    for(int index = 0; index < fuel.length; index++)
    {
        System.out.printf("%5d %5d %5d %5d %5d %5.2d %5.2d %5.2d %5.2d \n",
        fillUp1,days1,startMiles1,endMiles1,fuel[index].getDistance(),gallons1,fuel[index].returnMPG(),price1,fuel[index].getCost());
    }


}
}

我之前提到的问题已修复，但现在第 31 行出现错误 -System.out.printf("%5d %5d %5d %5d %5d %5.2d %5.2d %5.2d %5.2d\n",它编译得很好，但是当我尝试运行它时，出现错误“java.util.IllegalFormatPrecisionException: null(in java.util.Formatter$FormatSpecifier)”。这是什么意思？

Answer 1

您正在尝试创建测试类的实例(它没有您尝试调用的构造函数)，而不是您的 AnnualFuelUse 类。

改变

AnnualFuelUseTester[]fuel = {new AnnualFuelUseTester(1,1,45023,45231,10.00,2.95),
                                 new AnnualFuelUseTester(2,4,45231,45480,11.70,2.99),
                                 new AnnualFuelUseTester(3,8,45480,45659,9.30,3.01)};

至

AnnualFuelUse[] fuel = {new AnnualFuelUse(1,1,45023,45231,10.00,2.95),
                                     new AnnualFuelUse(2,4,45231,45480,11.70,2.99),
                                     new AnnualFuelUse(3,8,45480,45659,9.30,3.01)};