Working with Input and Output - Java 6 - page 404

This loop reads the entire file referenced by diskfile one byte at a time and displays
each byte, followed by a space character. It also displays -1 when the end of the file is
reached; you could guard against this easily with an if statement.

The ByteReader application in Listing 15.1 uses a similar technique to read a file input
stream. The input stream's close() method is used to close the stream after the last byte
in the file is read. Always close streams when you no longer need them; it frees system
resources.

LISTING 15.1 The Full Text of ByteReader.java

1: import java.io.*;
2:
3: public class ByteReader {
4: public static void main(String[] arguments) {
5: try {
6: FileInputStream file = new
7: FileInputStream(“class.dat”);
8: boolean eof = false;
9: int count = 0;
10: while (!eof) {
11: int input = file.read();
12: System.out.print(input + “ “);
13: if (input == -1)
14: eof = true;
15: else
16: count++;
17: }
18: file.close();
19: System.out.println(“\nBytes read: “ + count);
20: } catch (IOException e) {
21: System.out.println(“Error — “ + e.toString());
22: }
23: }
24: }

If you run this program, you'll get the following error message:

Error — java.io.FileNotFoundException: class.dat (The system
cannot find the file specified).

This error message looks like the kind of exception generated by the compiler, but it's
actually coming from the catch block in lines 20-22 of the ByteReader application. The
exception is being thrown by lines 6-7 because the class.dat file cannot be found.