minimum value method will return a negative number when i have an input validation that should stop negative numbers

Question

I have a method that determines the minumum value in an array. However, i have an if statement for an input validation that stops the user from entering negative numbers. However, when the user inputs a negative number the minimum value method stores that value when it should ignore it. I am not sure how to solve this, but i think it has something to do with the scope.

I have tried moving the methods around to different levels of scope.

import java.util.*;

public class Rainfall {

    public static void main(String[] args) {
        // set and intialize vairables
        double[] rainfall = new double[12];
        String[] months = {"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December" };
        double totalRainfall = 0;
        double averageRainfall = 0;
        double max = rainfall[0];

        // scanner to get user input
        Scanner scanner = new Scanner(System.in);

        // for loop to iterate through the months to get user input on rainfall each month
        for (int i = 0; i < rainfall.length; i++) {
            System.out.println(
                    "How much rainfall did you recieve, in inches, for the month of: " + months[i]);
            rainfall[i] = scanner.nextDouble();

            // if statement to reject negative numbers

            if (rainfall[i] < 0) {
                System.out.println("You can not enter a negative number");
                System.out.println("How much rainfall did you receive for the month of: " + months[i]);
                rainfall[i] = scanner.nextDouble();
            }

            // calculate total and average rainfall
            totalRainfall = rainfall[i] + totalRainfall;
        }
    }
}

I need the minimum value method to not store negative numbers.

Answer 1

Replace

if(rainfall[i] < 0)

with

while(rainfall[i] < 0)

This forces the user to input valid rainfalls.

Answer 2

You are adding the number in array first at this line rainfall[i] = scanner.nextDouble(); and then doing the check on negative number. So to resolve this store the input number in temp variable first and do the -ve check and then add into array like this:

Double temp = scanner.nextDouble();

        //while statement to reject negative numbers

        while (temp < 0) {
            System.out.println("You can not enter a negative number");
            System.out.println("How much rainfall did you recieve for the month of: " + months[i]);
            temp = scanner.nextDouble();
        }
        rainfall[i] = temp;