Java:查找数组中 double 的平均值

Question

我正在为我的 Java 入门类(class)做作业。作业的一部分是将文本文件中的 double 读入数组，然后使用不同的方法计算平均值。到目前为止，我已将 double 读入数组，但我不确定如何在另一种方法中引用该数组来计算平均值。我一直在网上搜索，但没有结果，可能是因为我糟糕的术语导致我得到不相关的答案。我从 netbeans 收到一个错误，指出无法找到符号 classGrades(因为它仅在 main 方法中。)我尝试将其定义为全局变量，但这不起作用，我们还没有了解这些，所以一定有另一种方法可以做到这一点。

总结一下:我不知道如何在方法之间引用变量。

这是我的代码

import java.io.File;
import java.util.Arrays;
import java.util.Scanner;

public class GradeChecker {

public static void main(String[] args) {
    // TODO code application logic here
    double[] classGrades = new double[76];
    double classAverage = calculateAverageGrade();


    fillArray(classGrades);
    for (int i = 0; i < classGrades.length; i++) {
        System.out.println(classGrades[i]);
    }
    //System.out.print(Arrays.toString(classGrades));
    System.out.print(classGrades.length);

}
    public static void fillArray(double[] ary) {
    try {
        File arrayInput = new File("ClassGrades.txt");
        Scanner in = new Scanner(arrayInput);
        in.useDelimiter("\r\n");

        int i = 0;
        while (in.hasNextLine()) {
            ary[i++] = in.nextDouble();
        }
        in.close();
    } catch (Exception exception) {
        System.out.println("Error: " + exception.getMessage());
    }
}

    private static double calculateAverageGrade(double[] classGrades) {
    double gradeSum = 0;
    double gradeAverage = 0;
    for (int i = 0.0; i < classGrades.length; i++) {
        gradeSum = gradeSum + classGrades[i];
    }
    gradeAverage = gradeSum/classGrades.length;
    return gradeAverage;
}
}

Answer 1

您可以将数组 classGrades 传递给函数:

    double[] classGrades = new double[76];
    double classAverage = calculateAverageGrade(classGrades);

这里:

import java.io.File;
import java.util.Arrays;
import java.util.Scanner;

public class GradeChecker {

    public static void main(String[] args) {
        // TODO code application logic here
        double[] classGrades = new double[76];
        double classAverage = calculateAverageGrade(classGrades);


        fillArray(classGrades);
        for (int i = 0; i < classGrades.length; i++) {
            System.out.println(classGrades[i]);
        }
        //System.out.print(Arrays.toString(classGrades));
        System.out.print(classGrades.length);

    }

    public static void fillArray(double[] ary) {
        try {
            File arrayInput = new File("ClassGrades.txt");
            Scanner in = new Scanner(arrayInput);
            in.useDelimiter("\r\n");

            int i = 0;
            while (in.hasNextLine()) {
                ary[i++] = in.nextDouble();
            }
            in.close();
        } catch (Exception exception) {
            System.out.println("Error: " + exception.getMessage());
        }
    }

    private static double calculateAverageGrade(double[] classGrades) {
        double gradeSum = 0;
        double gradeAverage = 0;
        for (int i = 0; i < classGrades.length; i++) {
            gradeSum = gradeSum + classGrades[i];
        }
        gradeAverage = gradeSum / classGrades.length;
        return gradeAverage;
    }
}