java计算数组的平均值
这是一个代码,用于获取用户输入的分数,查找其平均值、偏差,并以表格样式显示此信息。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,它表示平均值为0。我也这么做为什么我的老师教我们,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();
}
}
}
这是为好奇的人编辑的代码
导入java。util。扫描仪
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();
}
}
}
# 1 楼答案
实际上,您从未使用过
average
方法的返回结果。您可能打算将其传递给displayResults
,或者在main()
方法中将其分配给mean
# 2 楼答案
首先,你的平均方法应该更像这样:
没有理由将
mean
参数传递给average
方法。这就像将Dog
传递给createDog
方法一样但更重要的是,当您调用
average
时,您不会将结果存储在任何地方。你只是忽视了它如果您来自一个有指针的背景,请记住Java通过值传递原语——在方法内部更改
mean
,即double
,将不会影响方法外部的值。相反,你有因此
mean
为零的根本原因是您将其设置为零,并且从不更改它:# 3 楼答案
您已声明此方法以返回一个值:
但在main方法中,不使用返回的结果。然后打印出 另一个“平均值”变量的值,该变量是该函数的全局变量,且赋值为0
我想你想要:
# 4 楼答案
您正在返回
mean
值,但没有将方法调用average
的结果赋值给任何对象。您想要的是将方法的结果分配给变量:在
average
方法中,不需要将mean
作为参数,只需在本地声明并返回它# 5 楼答案
average(grades, mean);
将变量的副本发送到average()
方法。尽管名称相同,但average()
内的mean
变量与main()
内的mean
变量无关。要解决此问题,您需要执行以下操作我还建议您删除
mean
参数,并在average()
内声明一个局部变量。那你就做吧