BINARY I/O - Introduction to Java Programming: Comprehensive Version - page 686

The following statements create data streams. The first statement creates an input stream for
the file in.dat ; the second statement creates an output stream for the file out.dat .

DataInputStream input =
new DataInputStream( new FileInputStream( "in.dat" ));
DataOutputStream output =
new DataOutputStream( new FileOutputStream( "out.dat" ));

Listing 17.2 writes student names and scores to a file named temp.dat and reads the data back
from the file.

L ISTING 17.2

TestDataStream.java
1 import java.io.*;
2
3 public class TestDataStream {
4 public static void main(String[] args) throws IOException {

5 try ( // Create an output stream for file temp.dat

6 DataOutputStream output = output stream

7 new DataOutputStream( new FileOutputStream( "temp.dat" ));

8 ) {
9 // Write student test scores to the file
10 output.writeUTF( "John" );
11 output.writeDouble( 85.5 );
12 output.writeUTF( "Jim" );
13 output.writeDouble( 185.5 );
14 output.writeUTF( "George" );
15 output.writeDouble( 105.25 );
16 }
17
18

output

try ( // Create an input stream for file temp.dat

19 DataInputStream input =

input stream

20 new DataInputStream( new FileInputStream( "temp.dat" ));

21 ) {
22 // Read student test scores from the file
23 System.out.println(input.readUTF() + " " + input.readDouble());
24 System.out.println(input.readUTF() + " " + input.readDouble());
25 System.out.println(input.readUTF() + " " + input.readDouble());
26 }
27 }
28 }

input

John 85.5
Susan 185.5
Kim 105.25

A DataOutputStream is created for file temp.dat in lines 6 and 7. Student names and scores
are written to the file in lines 10-15. A DataInputStream is created for the same file in lines
19-20. Student names and scores are read back from the file and displayed on the console in
lines 23-25.
DataInputStream and DataOutputStream read and write Java primitive-type values
and strings in a machine-independent fashion, thereby enabling you to write a data file on one
machine and read it on another machine that has a different operating system or file structure.
An application uses a data output stream to write data that can later be read by a program using
a data input stream.
DataInputStream filters data from an input stream into appropriate primitive-type val-
ues or strings. DataOutputStream converts primitive-type values or strings into bytes and