Java Reference
In-Depth Information
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
FileInputStream(
"in.dat"
));
DataOutputStream output =
(
new
FileOutputStream(
"out.dat"
));
new
DataInputStream
new
DataOutputStream
Listing 19.2 writes student names and scores to a file named
temp.dat
and reads the data back
from the file.
L
ISTING
19.2
TestDataStream.java
1
import
java.io.*;
2
3
public class
TestDataStream {
4
public static void
main(String[] args)
throws
IOException {
5
// Create an output stream for file temp.dat
6
7
8
9
DataOutputStream output =
output stream
new
DataOutputStream(
new
FileOutputStream(
"temp.dat"
));
// Write student test scores to the file
10
11
12 output.writeUTF(
"Susan"
);
13 output.writeDouble(
185.5
);
14 output.writeUTF(
"Kim"
);
15 output.writeDouble(
105.25
);
16
17
// Close output stream
18 output.close();
19
20
output.writeUTF(
"John"
);
output
output.writeDouble(
85.5
);
close stream
// Create an input stream for file temp.dat
DataInputStream input =
21
22
23
24
// Read student test scores from the file
25 System.out.println( +
" "
+
);
26 System.out.println(input.readUTF() +
" "
+ input.readDouble());
27 System.out.println(input.readUTF() +
" "
+ input.readDouble());
28 }
29 }
input stream
new
DataInputStream(
new
FileInputStream(
"temp.dat"
));
input.readUTF()
input.readDouble()
input
John 85.5
Susan 185.5
Kim 105.25
A
DataOutputStream
is created for file
temp.dat
in lines 6-7. Student names and scores
are written to the file in lines 10-15. Line 18 closes the output stream. A
DataInputStream
is created for the same file in lines 21-22. Student names and scores are read back from the
file and displayed on the console in lines 25-27.
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.
