JAVA：查找双数组列表的平均值

Question

Trying to enter an arraylist of doubles into the console, then when the user ends the arraylist input with ctrl-z or d, find the average of the list of numbers they entered using doubles.

I'm getting lots of errors from this and im not sure why! any and all help is appreciated as I am a java beginner

public static void main(String[] args) {
    ArrayList<Double> numbers = new ArrayList<Double>();  

    Scanner in = new Scanner(System.in);   

    while (in.hasNextDouble())  
    {  
        Double input = in.nextDouble();  
        numbers.add(input);  
    }  

    in.close();

    for (Double element : numbers)  {  
        Double sum += element;
        System.out.println(sum/numbers.size()); 
    }
} 

Answer 1

To compute the final mean:

double sum = 0;
for(double d : numbers) {
    sum += d;
}
System.out.println(sum / numbers.size()); 

Answer 2

// don't miss the imports
import java.util.ArrayList;
import java.util.Scanner;

// you might have missed to add your main() method in a class
public class Average {
    public static void main(String[] args) {
        // This part was ok
        ArrayList<Double> numbers = new ArrayList<Double>();
        Scanner in = new Scanner(System.in);
        while (in.hasNextDouble()) {
            Double input = in.nextDouble();
            numbers.add(input);
        }
        in.close();

        // Forgot to initialize the value of sum
        Double sum = 0d;
        for (Double element : numbers) {
            // add the element
            sum += element;
            // don't count the average here
        }
        // count it outside the loop
        System.out.println(sum / numbers.size());
    }
}

Answer 3

Double sum += element;

That isn't legal syntax, you're trying to add something to a variable definition, which doesn't work. You're close though. Just declare the variable sum outside of the for loop.

double sum = 0;
for (double element : numbers)  {  
       sum += element;
   }
System.out.println(sum/numbers.size()); 

You also probably don't want to print out the current average every time so you should just move that to after the loop.

Answer 4

i have added java.util package which is required for Scanner and collections classes in your code main problem was in your for loop plz mark answer . thank you :)

import java.util.*;
    public class Test {

        public static void main(String[] args) {
            Double sum=0.0;
              ArrayList<Double> numbers = new ArrayList<Double>();  

              Scanner in = new Scanner(System.in);   

              while (in.hasNextDouble())  
              {  
                 Double input = in.nextDouble();  
                 numbers.add(input);  
              }  

               in.close();


                 for (Double element : numbers)  {  
                    sum += element;
            }
                   System.out.println(sum/numbers.size()); 

              } 

    }