java - Java中通过数组接受输入

Question

我试图让用户输入一组数字(=学生的分数)。另外，用户自己将决定数组的大小，即类(class)学生的数量。接受每个学生的分数后，我想将它们存储在一个数组中，显示所有学生的分数，并计算类(class)的平均分。稍后将谈到平均部分。 有人可以帮我解决这段(显然是错误的)代码吗，谢谢!!

package chapter2.Arrays;
import java.util.*;

public class Arrays_ExampleOne {

static int size;
static int marks;
static int [] numbers=new int [size];
static Scanner in=new Scanner(System.in);


public static void main(String[] args) {
    // TODO Auto-generated method stub

    System.out.println("Welcome to Cincinnati Elementary");
    System.out.println("Class report details for ");
    System.out.println("Enter the number of students in the class");
    size=in.nextInt();
    System.out.println("Enter the marks of each student");
    for(int i=0;i<=size;i++)
    {
    numbers[i]=in.nextInt();    
    }

/*  System.out.println("The marks of all students are"+ " ");
    {
    for(int i=0;i<=size;i++)
    {
        System.out.print(numbers[i]);
    }
    System.out.println();

    }
    //int avg=
    */}
}

================================================== ===========

修改了代码，希望在 main 之外创建一个函数来计算数组的平均值:

package chapter2.Arrays;
import java.util.*;

public class Arrays_ExampleOne {

/*static int size;
static int marks;
static int [] numbers=new int [size];*/
static Scanner in=new Scanner(System.in);


    public static void main(String[] args) {
        // TODO Auto-generated method stub

        System.out.println("Welcome to Cincinnati Elementary");
        System.out.println("Class report details for ");
        System.out.println("Enter the number of students in the class");
        int size;
        //static int marks;
        //static int [] numbers=new int [size];

        size=in.nextInt();

        int [] numbers=new int [size];
        System.out.println("Enter the marks of each student");
        for(int i=0;i<size;i++)
        {
        numbers[i]=in.nextInt();    
        }

        System.out.println("The marks of all students are:"+ " ");
        {
        for(int temp:numbers)
        {
            System.out.print(temp+ " ");
        }
        System.out.println();
        }

        int arraySize=numbers.length;
        int arraySum=0;
        //Calculate the sum of array elements
        for(int temp1:numbers)
        {
            arraySum+=temp1;
        }

        int average=arraySum/arraySize;

        System.out.println("The average of all the students scores is:"+ " "+average);
    }

    /*public int calculateAverage(int array[])
    {
        int arraySize=array.length;

    }*/
}

================================================== =============== 在 main 之外添加了用于计算平均值的单独代码。

package chapter2.Arrays;
import java.util.*;

public class Arrays_ExampleOne {

/*static int size;
static int marks;
static int [] numbers=new int [size];*/
static Scanner in=new Scanner(System.in);


    public static void main(String[] args) {
        // TODO Auto-generated method stub

        Arrays_ExampleOne obj=new Arrays_ExampleOne();
        System.out.println("Welcome to Cincinnati Elementary");
        System.out.println("Class report details for ");
        System.out.println("Enter the number of students in the class");
        int size;
        //static int marks;
        //static int [] numbers=new int [size];

        size=in.nextInt();

        int [] numbers=new int [size];
        System.out.println("Enter the marks of each student");
        for(int i=0;i<size;i++)
        {
        numbers[i]=in.nextInt();    
        }

        System.out.println("The marks of all students are:"+ " ");
        {
        for(int temp:numbers)
        {
            System.out.print(temp+ " ");
        }
        System.out.println();
        }

    /*  int arraySize=numbers.length;
        int arraySum=0;
        //Calculate the sum of array elements
        for(int temp1:numbers)
        {
            arraySum+=temp1;
        }

        int average=arraySum/arraySize;

        System.out.println("The average of all the students scores is:"+ " "+average);*/
        int average=obj.calculateAverage(numbers);
        System.out.println("The average of all the students is:"+ " "+average);
    }

    public int calculateAverage(int array[])
    {
        int arraySize=array.length;
        int arraySum=0;
        for(int temp: array)
        {
        arraySum+=temp;
        }

        int average=arraySum/arraySize;

        return average;
    }
}

Answer 1

首先，您应该要求用户先输入大小，然后设置数组大小:

static int size;
static int marks;
static Scanner in=new Scanner(System.in);

public static void main(String[] args) {
    System.out.println("Enter number of student:");
    size = in.nextInt();
    int [] numbers=new int [size];

    //the rest of your code goes here
}

注意:小心你的 for 循环:

for(int i=0;i<=size;i++){
             ^
    numbers[i]=in.nextInt();
}

结果是ArrayIndexOutOfBoundException因为您正在尝试访问索引 size 处的元素，其中最大值 index n 大小的数组为 n-1 。 应该是 <而不是<=

对于方法calculateAverage，它应该如下所示:

public static double calculateAverage(int array[])
{
    double sum=0.0;
    for(int i=0;i<array.length;i++){
       sum+=array[i];
    }
    return sum / array.length;
}

请注意，此方法应该是静态的，因为您想在静态方法中使用它，并且平均始终处理 double/float数据类型，而不是 int

从 main 方法中，您可以这样调用它:

System.out.println("Average marks:"+calculateAverage(numbers));