Question

所以我有一个作业，我应该创建一个程序，该程序生成100个随机整数并将它们存储在一个一维数组中。然后，我应该计算平均值，标准偏差和方差。通过大量的试验和错误，我能够制作出一个执行此操作的程序，但是我错过的是它说为每个属性（平均值，标准偏差和方差）编写一个单独的方法。我该怎么做？

package homeassignment5;


public class HomeAssignment5 {

    public static void main(String[] args) {
        int n;
        n = 100;
     int[] random = new int [n];
     for (int i = 0; i<random.length; i++)
         random[i] = (int) (Math.random()* n);
         double total = 0;
         double average = 0;
         double variance = 0;
         double var = 0;
         double sd = 0;

         for (int element : random){
             total += element;
             average = total/n;
         }
         for (int i = 0; i<random.length; i++){
             variance += (random[i] - average) * (random[i] - average);
         }
             var = variance / random.length;
             sd = Math.sqrt(var);


    //System.out.println("Total is: " + total);
     System.out.println("Average is: " + average);
     System.out.println("Variance is " + var);
     System.out.println("Standard deviation is " + sd);

     /*for (int i = 0; i<random.length; i++)
         System.out.println(random[i]);
         */

    }


}

可能有点混乱，但是我对Java真的很陌生，这是大量试验和错误的产物。

Answer 1

我相信这会对您有所帮助。所有功能都以方法形式分开，初始化是分开的。

**欢迎使用**

public class Refactor {

    private int[] random;
    private int n;
    private double total = 0;
    private double average = 0;
    private double variance = 0;
    private double sd = 0;

    public Refactor(int n) {
        this.n = n;
        this.populateArray();
    }

    private void populateArray() {
        random = new int[n];
        for (int i = 0; i < random.length; i++)
            random[i] = (int) (Math.random() * n);
    }

    public double getAverage() {
        average = 0;
        total = 0;
        for (int element : random) {
            total += element;
        }
        average = total / n;
        return average;
    }

    public double getVariance() {
        variance = 0;
        for (int i = 0; i < random.length; i++) {
            variance += (random[i] - average) * (random[i] - average);
        }
        variance = variance / random.length;
        return variance;
    }

    public double getSD() {
        this.getVariance();
        sd = 0;
        sd = Math.sqrt(variance);
        return sd;
    }

    public static void main(String[] args) {
        Refactor ref = new Refactor(100);
        System.out.println("Average is: " + ref.getAverage());
        System.out.println("Variance is " + ref.getVariance());
        System.out.println("Standard deviation is " + ref.getSD());
    }
}

Answer 2

因此，有几种解决方法，但是最简单的方法可能是：

public class HomeAssignment5 {
    private static int[] random;

    public static void main(String[] args){
        random = = new int[100];
        ...
    }

    public static void getAverage(){
    // void if you want to print it here, double if you want to print in main
        double average = 0;
        int total = 0;

        for(int i = 0; i < 100; i += 1)
            total += random[i];

        average = total / n; // you'll want to do this outside of the loop to
                             // to get the correct result!
        System.out.println("Average: " + average);

    }

    ...
}

您也可以将数组作为参数传递给每个方法。
顺便说一句，在这里发布的内容中，您实际上尚未向该数组中写入任何随机数，因此请记住要这样做，它目前仍为零。

Answer 3

如何将数组传递给每个方法？

这三种方法中第一个也是最简单的方法是average：

    static double average(int [] r)
    {   double total = 0;
        for (int e: r) total += e;
        return total/r.length;
    }

对于第二种方法，标准偏差，我建议不要传递数组，而应传递方差，因为如果程序无论如何都计算了方差，则无需重新计算，如果没有，则可以使用对方差方法的调用作为参数来调用SD方法。

    static double SD(double variance) { return Math.sqrt(variance); }

对于第三个方法，即方差，我建议不仅传递数组，而且还要传递其平均值，其推理与上述类似。

    static double variance(int [] r, double average)
    {   double var = 0;
        for (int e: r) var += (e - average) * (e - average);
        return var/r.length;
    }

定义了这三种方法后，您现在可以替换

         double total = 0;
         double average = 0;
         double variance = 0;
         double var = 0;
         double sd = 0;

         for (int element : random){
             total += element;
             average = total/n;
         }
         for (int i = 0; i<random.length; i++){
             variance += (random[i] - average) * (random[i] - average);
         }
             var = variance / random.length;
             sd = Math.sqrt(var);

使用

     double average = average(random);
     double var = variance(random, average);
     double sd = SD(var);

如何将我的代码分成不同的方法

3 个答案: