BINARY I/O - Introduction to Java Programming: Comprehensive Version - page 683

15 // Create an input stream for the file
16 FileInputStream input = new FileInputStream( "temp.dat" );
17 ) {
18 // Read values from the file
19 int value;
20 while ((value = input.read()) != -1 )
21 System.out.print(value + " " );
22 }
23 }
24 }

input stream

input

1 2 3 4 5 6 7 8 9 10

The program uses the try-with-resources to declare and create input and output streams
so that they will be automatically closed after they are used. The java.io.InputStream
and java.io.OutputStream classes implement the AutoClosable interface. The
AutoClosable interface defines the close() method that closes a resource. Any object of
the AutoClosable type can be used with the try-with-resources syntax for automatic closing.
A FileOutputStream is created for the file temp.dat in line 7. The for loop writes
ten byte values into the file (lines 10-11). Invoking write(i) is the same as invoking
write((byte)i) . 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 17.8.

AutoClosable

end of a file

Binary data

F IGURE 17.8

A binary file cannot be displayed in text mode.

Tip
When a stream is no longer needed, always close it using the close() method or
automatically close it using a try-with-resource statement. 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