Code
/// Name: JJ Deng
/// Period: 6
/// Program Name:SummingThreeNumbers
/// File Name: ThreeNumber.java
/// Date Finished: 5/29/2016
import java.io.File;
import java.util.Scanner;
public class ThreeNumber {
public static void main(String[] args) throws Exception
{
int a, b, c, sum;
String fileName = "3nums.txt";
Scanner keyboard = new Scanner(System.in);
System.out.print("Reading numbers from file \"" + fileName + "\":\n\n>");
Scanner fileIn = new Scanner(new File(fileName));
a = fileIn.nextInt();
b = fileIn.nextInt();
c = fileIn.nextInt();
fileIn.close();
System.out.println("done.");
sum = a + b + c;
System.out.println(a + " + " + b + " + " + c + " = " + sum);
}
}
Picture of the output