java - 计算数组的平均值

Question

这是一段代码，用于获取用户估算的成绩，找到其平均值、偏差，并以表格形式显示此信息。我的程序接受用户输入并很好地显示信息，但它无法正确计算平均值和偏差。运行时，它说平均值为0。我正在按照老师教我们的方式做，但我找不到我的错误。

import java.util.Scanner;

public class ClassScores{
public static void main(String[] args){
String[] names = {"Bashful","Doc","Dopey","Grumpy","Happy","Sleepy","Sneezy"};
double[] grades = new double[7];
double mean=0;
double[] difference = new double[7];

getScores(grades);
average(grades, mean);
deviation(grades,mean,difference);
displayResults(names, grades, difference, mean);
} 



public static double[] getScores(double[] grades)
{
Scanner kb= new Scanner(System.in);
System.out.println("Enter grades for students in alphabetical order.");
for (int i=0;i<grades.length; i++)
{
    grades[i]=kb.nextDouble();
}
return grades;  
}

public static double average(double[] grades, double mean)
{
double total = 0;
for (double i : grades)
{
    total += i;
}
if (grades.length>0)
{
    mean = total/grades.length;
}
return mean;
}

public static double[] deviation(double[] grades, double mean, double[] difference)
{
for (int i=0; i<grades.length; i++)
{
    difference[i]=grades[i]-mean;
}
return difference;
}

public static void displayResults(String[] names, double[] grades, double[] difference, double mean)
{
System.out.println("The average score is" +mean);
System.out.println("Student Name   Grade    Mean Deviation");

for (int i=0; i<names.length; i++)
{
    System.out.printf(names[i]);
    System.out.printf("%20f", grades[i]);
    System.out.printf("%20f", difference[i]);
    System.out.println();
}

}   

}

这是为好奇的人提供的编辑后的代码。

导入java.util.Scanner;

public class ClassScores{
public static void main(String[] args){
String[] names = {"Bashful","Doc","Dopey","Grumpy","Happy","Sleepy","Sneezy"};
double[] grades = new double[7];
double mean=0;
double[] difference = new double[7];

getScores(grades);
mean = average(grades);
deviation(grades,mean,difference);
displayResults(names, grades, difference, mean);
}



public static double[] getScores(double[] grades)
{
Scanner kb= new Scanner(System.in);
System.out.println("Enter grades for students in alphabetical order.");
for (int i=0;i<grades.length; i++)
{
    grades[i]=kb.nextDouble();
}
return grades;  
}

public static double average(double[] grades)
{
double total = 0;
for (double i : grades)
{
    total += i;
}
return total/(grades.length);
}

public static double[] deviation(double[] grades, double mean, double[] difference)
{
for (int i=0; i<grades.length; i++)
{
    difference[i]=grades[i]-mean;
}
return difference;
}

public static void displayResults(String[] names, double[] grades, double[] difference, double mean)
{
System.out.println("The average score is" +mean);
System.out.println("Student Name   Grade    Mean Deviation");

for (int i=0; i<names.length; i++)
{
    System.out.printf(names[i]);
    System.out.printf("%20f", grades[i]);
    System.out.printf("%20f", difference[i]);
    System.out.println();
}

}   

}

Answer 1

您从未真正使用过average方法的返回结果。您可能打算将其传递给 displayResults，或将其分配给 main() 方法中的 mean。