import java.io.*;
import java.util.Scanner;

public class FileInputOutput {

    public static void main(String[] args) {

        String[] fileContents = getFileContents("nums.txt");

        // print contents
        for (int i = 0; i < fileContents.length; i++) {
            System.out.println("Line " + i + ": " + fileContents[i]);
        }

        // write to file
        writeArrayToFile("output.txt", fileContents);

        // sum values
        System.out.println("The sum of the values is " + sumIntegers(fileContents));
    }

    // add all numbers in the array
    public static int sumIntegers(String[] array) {
        int sum = 0;

        /* write missing code here */

        return sum;
    }

    // read file into array
    public static String[] getFileContents(String fileName) {
        String[] contents = null;
        int count = 0;

        try {
            // first pass: count lines
            Scanner scanner = new Scanner(new File(fileName));
            while (scanner.hasNextLine()) {
                scanner.nextLine();
                count++;
            }
            scanner.close();

            // create array
            contents = new String[count];

            // second pass: read lines
            scanner = new Scanner(new File(fileName));
            for (int i = 0; i < count; i++) {
                contents[i] = scanner.nextLine();
            }
            scanner.close();

        } catch (Exception e) {
            System.out.println("File Input Error");
        }

        return contents;
    }

    // write array to file
    public static void writeArrayToFile(String fileName, String[] array) {
        try {
            PrintWriter writer = new PrintWriter(fileName);

            for (int i = 0; i < array.length; i++) {
                writer.println(array[i]);
            }

            writer.close();

        } catch (Exception e) {
            System.out.println("File Output Error");
        }
    }
}