Question

Write a java program that creates a file called numbers.txt that uses the PrintWriter class. Write the odd numbers 1 to 99 into the file. Close the file.

Using Scanner, open the numbers.txt file and read in the numbers. Add them all up and print the total. Close the file.

Answer 1

import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintWriter;
import java.util.Scanner;

public class OddSumFile {

    public static void main(String[] args) throws FileNotFoundException {
        PrintWriter pw = new PrintWriter("numbers.txt");
        for (int i = 1; i < 100; i += 2) {
            pw.println(i);
        }
        pw.close();

        File file = new File("numbers.txt");    // read a file and create a file.
        Scanner fin = new Scanner(file);    // create a scanner to read from file
        int sum = 0;
        while (fin.hasNextInt()) {
            sum += fin.nextInt();
        }
        System.out.println(sum);
        fin.close();    // close file.
    }
}