Question

我正在做这个按行星计算重量的程序。我必须显示一个包含3列，行星名称，重力值和权重的图表。我正在尝试执行此程序，但我总是将重力值的输出设为NaN，并将所有重量值的输出设为0.0。

这是我的代码：

import java.util.Scanner;
import java.io.File;
import java.io.IOException;
import java.util.InputMismatchException;
import java.io.FileNotFoundException;
import java.io.PrintWriter;
import java.io.FileWriter;
public class WeightOnPlanetsV1
{
    public static double[] getGravity( ) throws IOException {
        Scanner fileScanner = new Scanner(new File("output.txt"));
        double[] Gravity = new double[8];
        double[] abc = new double[8];
        for(int i = 0; i < 8; i++)
        {
            abc[i] = fileScanner.nextDouble();
            Gravity[i] = abc[i] / 9.79211720754188E34;
        }
        fileScanner.close();
        return Gravity;
    }
    public static double[] calcWeight(){
        double earthWeight =100.0;
        double[] Weight = new double[8];
        double[] Gravity = new double[8];
        double[] mass = new double[8];
        for(int a = 0; a < 8; a++){
            mass[a] = (earthWeight * 433.59237) / Gravity[a];
            Weight[a] = mass[a] * Gravity[a];
    }
    return Weight;
}
public static void PrintResults( ) throws IOException{
    double[] Gravity = calcWeight();
    double[] Weight = new double[8];
    String[] planets = new String[8];
    planets[0] = "Mercury";
    planets[1] = "Venus";
    planets[2] = "Earth";
    planets[3] = "Mars";
    planets[4] = "Jupiter";
    planets[5] = "Saturn";
    planets[6] = "Uranus";
    planets[7] = "Neptune";
        Scanner in = new Scanner(System.in);
        System.out.print("Please enter your weight in pounds: ");
        double weightonEarth = in.nextDouble();
        System.out.println();
        System.out.println("        My weight on the Planets        ");
        System.out.println();
            System.out.printf("%10s     %9s     %8s", "Planet",    "Gravity",     "Weight on planet(lbs)");
        System.out.println();
        System.out.println("-------------------------------------------   -------");
         for(int y = 0; y < 8 ; y++)
           {

               System.out.printf("%-11s", planets[y]);     
               System.out.printf("%13.2f", Gravity[y]); 
               System.out.printf("%20.2f\n",Weight[y]);
        }

}
}

这是我的输出值

3.681794655084276E34
8.863175348783772E34
9.79211720754188E34
3.6956542096917174E34
2.476892445877445E35
6.032365515665391E31
8.863553576713065E34
1.11374098023869E35

我真的很感激任何帮助！

Answer 1

您的重力值是根据以下计算的：

double[] Gravity = calcWeight();

在calcWeight()内，您返回一个double[] Weight数组，该数组的计算公式为：

Weight[a] = mass[a] * Gravity[a];

正如@Thomas正确指出的那样，您实际上从未向Gravity[]分配任何值，因为永远不会调用getGravity()。因此，每个Weight值的分母将为零，即这是除以零，我认为这是NaN Gravity值的原因。

在PrintResults()内，永远不会定义Weight[]数组，因此它们都是零。

如何修复代码：

您可以尝试使用以下内容：

public static double[] getGravity() throws IOException {
    // same as before
}

// pass the already-computed gravity array to this method
public static double[] calcWeight(double[] gravity) {
    double earthWeight = 100.0;
    double[] weight = new double[8];
    double[] mass = new double[8];

    for (int a=0; a < 8; a++) {
        mass[a] = (earthWeight * 433.59237) / gravity[a];
        weight[a] = mass[a] * gravity[a];
    }
    return weight;
}

public static void PrintResults() throws IOException {
    double[] Gravity = getGravity();
    double[] Weight = calcWeight();

    // keep the rest as is
}

Answer 2

您没有在任何地方致电script is out of range。相反，你正在为重力分配权重：

getGravity

通过用以下代码替换行来修复它：

double[] Gravity = calcWeight();

需要有关Java程序的帮助来计算行星上的权重

2 个答案: