可以通过扫描仪输入循环吗？

Question

I've just started learning java and I can't seem to find a way to use for loop for a simple user input. Let's say that I have to enter an unknown number of hw scores, but I don't know it until the user actually enters it in. The problem is that I have to be add the scores the user entered. How do I go about looping the Scanner portion of the problem.

import java.util.Scanner;

public class HomeworkCalculator {

public static void main(String[] args) {

Scanner scanner = new Scanner(System.in);

System.out.println("Please enter the homework scores:");
double hwScores = scanner.nextDouble();

//how can I loop through the number of homework added on plus 
//add the sum and find the average?

Answer 1

You can use scanner without loop in here.(with a loop is also possible ). you can try in this way.

Scanner scanner = new Scanner(System.in);
System.out.println("Please enter the homework scores in" 
                                          +"a single line by separate by space");
List<Double> list = new ArrayList<>();
String str = scanner.nextLine();
for(String i:str.split(" ")){
   list.add(Double.parseDouble(i));
}
System.out.println(list);

Inputs:

45 58 5 5 66 1

Out put:

[45.0, 58.0, 5.0, 5.0, 66.0, 1.0]

Next part of your question is about finding the average.

You can find the sum by adding all elements of List , and divide sum by number of elements in the List

Answer 2

You can use a for loop fot the input. It would good sense to define the scanner in the for loop because you only need the scanner in the loop, but java syntax makes the result ugly, so define it before the loop:

double total = 0.0;
int count = 0;
System.out.println("Please enter the homework scores (negative to end):");
Scanner scanner = new Scanner(System.in); 
for (double score = scanner.nextDouble(); score > 0; score = scanner.nextDouble()) {
    total += score;
    count ++;
    scanner.next(); // you need this to clear the newline from the buffer
}
double average = total / count;