Chapter 17 Exercise 3, Introduction to Java Programming, Tenth Edition Y. Daniel LiangY.

17.3 (Sum all the integers in a binary data file)
Suppose a binary data file named Exercise17_03.dat
has been created and its data are created using writeInt(int)
in DataOutputStream. The file contains an unspecified number
of integers. Write a program to find the sum of the integers.

import java.io.*;

public class Exercise_03 {

    public static void main(String[] args) throws IOException {

        // Get the file for this exercise
        File file = new File("Exercise17_03.dat");

        // if file doesn't exist create the file and write a random number of integers
        if (!file.exists() || true) {
            try (DataOutputStream out =
                         new DataOutputStream(new BufferedOutputStream(new FileOutputStream(file)))) {

                int random = (int) (Math.random() * 200);

                for (int i = 0; i < random; i++) {
                    out.writeInt((int)(Math.random() * 200));
                }
            }
        }

        // Read the file and display the sum
        try (DataInputStream input = new DataInputStream(new BufferedInputStream(new FileInputStream(file)))) {

            int sum = 0;
            int count = input.available() / 4;
            System.out.println(count);
            while (count > 0) {
                sum += input.readInt();
                count--;
            }
            System.out.println("The sum is " + sum);
        }


    }
}