Java 计算 MPG 误差

Question

我在这个作业中遇到了问题，我应该计算某个输入变量的每加仑英里数。

作业的规格是：http://www.mrferrante.com/apcs/WebLessons/LessonA4/images/Lab_A1_fig_1.gif

我应该计算 MPG

这是我的 Driver:

public class Driver{
        public static void main(String[] args){
        int odometerReading = 15;    
        P4_Icel_Murad_Car auto = new P4_Icel_Murad_Car(odometerReading);

        System.out.println("New car odometer reading: " + startMiles);
        auto.fillUp(150,8);
        System.out.println("Miles per gallon: " + auto.calculateMPG());
        System.out.println("Miles per gallon: " + auto.calculateMPG());
        auto.resetMPG();
        auto.fillUp(350, 10);
        auto.fillUp(450, 20);
        System.out.println("Miles per gallon: " + auto.calculateMPG());
        auto.resetMPG();
        auto.fillUp(603, 25.5);
        System.out.println("Miles per gallon: " + auto.calculateMPG());

    }
}

下面是代码的其余部分：

public class P4_Icel_Murad_Car{
    private int myStartMiles;
    private int myEndMiles;
    private double myGallonsUsed;
    public int P4_Icel_Murad_Car(int odometerReading){
     myStartMiles = odometerReading;
     return myStartMiles;
    }
    public void fillUp(int odometerReading,double gallons){
        int Miles = odometerReading - myStartMiles;
        double MilesPerGallon = Miles / gallons;
    }
    public double calculateMPG( int odometerReading, double gallons){
        int MPG = (int)(odometerReading/gallons);
        return MPG;
    }
    public void resetMPG(){
        myStartMiles = 0;
        myEndMiles = 0;
        myGallonsUsed = 0;
    }
}

当输入15作为startMiles时，结果应该是

New car odometer reading: 15
    Miles per gallon: 16.875
    Miles per gallon: 16.875
    Miles per gallon: 10.0
    Miles per gallon: 6.0

但是我正在使用的 IDE (BlueJ) 声称 P4_Icel_Murad_Car() 不需要任何参数并且我正在放入 int 而不是什么都没有。提前感谢您的帮助！

Answer 1

你的 class 叫做 P4_Icel_Murad_Car。

所以 P4_Icel_Murad_Car 应该是 class 的构造函数，你不能从它 return 一个 int。

尝试将该方法替换为：

    public P4_Icel_Murad_Car(int odometerReading){
         myStartMiles = odometerReading;
    }

Answer 2

你的代码有几个错误，这里是带注释的工作版本：

public static class P4_Icel_Murad_Car {
    private int myStartMiles;
    private int myEndMiles;
    private double myGallonsUsed;

    public P4_Icel_Murad_Car(final int odometerReading) { // Constructor does not have return type, do not put int before constructor name
        this.myStartMiles = odometerReading;
        this.myEndMiles = odometerReading; // init end miles with start miles from the start
        this.myGallonsUsed = 0;
    }

    public void fillUp(final int odometerReading, final double gallons) {
        this.myEndMiles = odometerReading; // store current odometer
        this.myGallonsUsed += gallons; // sum up gas
    }

    public double calculateMPG() { // calculate mileage, divide by gallons
        return (this.myEndMiles - this.myStartMiles) / this.myGallonsUsed;
    }

    public void resetMPG() { // reset means start from current odometer reading
        this.myStartMiles = this.myEndMiles;
        this.myGallonsUsed = 0;
    }
}

Java 计算 MPG 误差

Java Calculating MPG Error

java

math

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driver

syntax-error