File Processing - Building Java Programs: A Back to Basics Approach - page 379

Here's how to modify the header for the main method to include a throws clause
indicating that it may throw a FileNotFoundException :

public static void main(String[] args)
throws FileNotFoundException {
Scanner input = new Scanner(new File("hamlet.txt"));
...

}

With the throws clause, the line becomes so long that we have to break it into two
lines to allow it to fit in the margins of the textbook. On your own computer, you will
probably include all of it on a single line.
After this modification, the program compiles. Once you've constructed the Scanner
so that it reads from the file, you can manipulate it like any other Scanner . Of course,
you should always prompt before reading from the console to give the user an indication
of what kind of data you want, but when reading from a file, you don't need to prompt
because the data is already there, stored in the file. For example, you could write a pro-
gram like the following to count the number of words in Hamlet :

1 // Counts the number of words in Hamlet.
2
3 import java.io.*;
4 import java.util.*;
5
6 public class CountWords {
7 public static void main(String[] args)
8 throws FileNotFoundException {
9 Scanner input = new Scanner( new File("hamlet.txt"));
10 int count = 0;
11 while (input.hasNext()) {
12

String word = input.next();

13 count++;

14 }
15 System.out.println("total words = " + count);
16 }
17 }

Note that you have to include an import from java.util for the Scanner class
and an import from java.io for the File class. The program generates the follow-
ing output:

total words = 31956