BINARY I/O - Introduction to Java Programming - page 715

15 // Create an input stream for the file

FileInputStream input = new FileInputStream( "temp.dat" );

16
17
18 // Read values from the file
19 int value;
20 while ((value = ) != -1 )
21 System.out.print(value + " " );
22
23

input stream

input.read() input

// Close the output stream

input.close();

24
25 }
26 }

1 2 3 4 5 6 7 8 9 10

A FileOutputStream is created for the file temp.dat in line 6. The for loop writes ten
byte values into the file (lines 9-10). Invoking write(i) is the same as invoking
write((byte)i) . Line 13 closes the output stream. Line 16 creates a FileInputStream
for the file temp.dat . Values are read from the file and displayed on the console in lines
19-21. The expression ((value = input.read()) != -1) (line 20) reads a byte from
input.read() , assigns it to value , and checks whether it is -1 . The input value of -1
signifies the end of a file.
The file temp.dat created in this example is a binary file. It can be read from a Java pro-
gram but not from a text editor, as shown in Figure 19.8.

end of a file

Binary data

F IGURE 19.8

A binary file cannot be displayed in text mode.

Tip
When a stream is no longer needed, always close it using the close() method. Not
closing streams may cause data corruption in the output file, or other programming
errors.

close stream

Note
The root directory for the file is the classpath directory. For the example in this topic, the
root directory is c:\book , so the file temp.dat is located at c:\book . If you wish to
place temp.dat in a specific directory, replace line 6 with

where is the file?

FileOutputStream output =
new FileOutputStream ( "directory/temp.dat" );

Note
An instance of FileInputStream can be used as an argument to construct a
Scanner , and an instance of FileOutputStream can be used as an argument to
construct a PrintWriter . You can create a PrintWriter to append text into a
file using

appending to text file