java-错误不兼容的类型：意外的返回值-遍历列表

Question

I am asked to write code that will display the total sum of the integers in the numbers list. I am to make use of the total variable that has already been declared for me and use a for loop to iterate through the elements of the list.

The issue is I keep getting the error incompatible types: unexpected return value.' When I try changing void in the main method to int, I get the error 'void type not allowed here.' Any ideas on how to fix this?

import java.util.ArrayList;

public class ArrayListTestProgram {
    public static void main(String args[]) {
        int                     total = 0;
        ArrayList<Integer>      numbers;
        numbers = new ArrayList<Integer>(); 
        numbers.add(1);
        numbers.add(45);
        numbers.add(23);
        numbers.add(87);
        numbers.add(89);
        numbers.add(213); 
        System.out.println("The ArrayList looks like this: " + numbers);
        System.out.println("It has " + numbers.size() + " elements in it");
        System.out.println("The 5th element in it is: " + numbers.get(4));
        int sum = 0;


        for (int i = 0; i < numbers.size(); i++) {
          sum += numbers.get(i);
          return sum;

        }
        System.out.println(sum);

    }
}

Answer 1

Remove the return line:

for (int i = 0; i < numbers.size(); i++) {
    sum += numbers.get(i);
//  return sum;
}

Your main has return type void and you are returning an int .

Answer 2

You can`t set return type for main() metod. It should be void. You can create new static metod

public static giveMeSumOfList(List<Integer> list){
int sum = 0; 
for (int i = 0; i < list.size(); i++) {
          sum += numbers.get(i);
          return sum;
        }

After you can call this metod from main and other static metods.

Answer 3

Remove print around System.out.println(sum) and remove return sum

import java.util.ArrayList;

public class ArrayListTestProgram {
    public static void main(String args[]) {
        int total = 0;
        ArrayList<Integer> numbers;
        numbers = new ArrayList<Integer>();
        numbers.add(1);
        numbers.add(45);
        numbers.add(23);
        numbers.add(87);
        numbers.add(89);
        numbers.add(213);
        System.out.println("The ArrayList looks like this: " + numbers);
        System.out.println("It has " + numbers.size() + " elements in it");
        System.out.println("The 5th element in it is: " + numbers.get(4));
        int sum = 0;


        for (int i = 0; i < numbers.size(); i++) {
            sum += numbers.get(i);

        }
        System.out.println(sum);

    }
}