File Processing - Building Java Programs: A Back to Basics Approach - page 390

9 System.out.println("This program will add a series");
10 System.out.println("of numbers from a file.");
11 System.out.println();
12
13 Scanner console = new Scanner(System.in);
14 System.out.print("What is the file name? ");
15 String name = console.nextLine();
16 Scanner input = new Scanner( new File(name));
17 System.out.println();
18
19 double sum = 0.0;
20 int count = 0;
21 while (input.hasNextDouble()) {
22 double next = input.nextDouble();
23 count++;
24 System.out.println("number " + count + " = " + next);
25 sum += next;
26 }
27 System.out.println("Sum = " + sum);
28 }
29 }
Notice that the program has two different Scanner objects: one for reading from
the console and one for reading from the file. We read the file name using a call on
nextLine to read an entire line of input from the user, which allows the user to type
in file names that have spaces in them. Notice that we still need the throws
FileNotFoundException in the header for main because even though we are
prompting the user to enter a file name, there won't necessarily be a file of that name.
If we have this program read from the file numbers.dat used earlier, it will pro-
duce the following output:
This program will add a series
of numbers from a file.
What is the file name? numbers.dat
number 1 = 308.2
number 2 = 14.9
number 3 = 7.4
number 4 = 2.8
number 5 = 3.9
number 6 = 4.7
number 7 = -15.4
number 8 = 2.8
Sum = 329.29999999999995