Java 天地·Core Java·Lecture Notes·Unit 10 - Applications, File Handling and Exceptions

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Example of reading bytes from a FileInputStream

Consider a text file example1.txt containing the following:

A
B
C

We can write a program to display the numeric value of each byte in this file. The output of the file is as follows:

The bytes with values 13 and 10 correspond the characters to carriage return ( <cr> ) and new-line ( <nl> ) respectively (which are how the Windows system indicates a new line in a text file).

Java actually views this file as a stream of bytes as follows:

‘A’

<cr>

<nl>

‘B’

<cr>

<nl>

‘C’

end of file

The listing of the application to generate this output is as follows:

import java.io.*;
public class FileTest2
{
public static void main( String args[] )
    {
    String fileName = "example.txt";
    File f1 = new File( fileName );
    FileInputStream stream;
    int b;
    try
      {
      stream = new FileInputStream(f1);
      for( int i = 0; i < f1.length(); i++)
        {
        // get next byte
        try
          {
          b = stream.read();
          // display byte with message on screen
          System.out.println("Byte " + i + " = ‘" + b + "‘");
          }
        catch (IOException e) {}
        }
      }
    catch (FileNotFoundException fileException) {}
    }
} // class

Ignore the ‘try’ and ‘catch’ statements for now — these are related to dealing with exceptional conditions, such as the file not being found. Exceptions, file related and otherwise, are covered later in this unit.

This application is given to illustrate how stream , an object of the FileInputStream

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