Java Reference
In-Depth Information
RandomAccessFile
. A large case study of using
RandomAccessFile
to organize an
address book is given in Supplement VI.B.
L
ISTING
19.8
TestRandomAccessFile.java
1
import
java.io.*;
2
3
public class
TestRandomAccessFile {
4
public static void
main(String[] args)
throws
IOException {
5
// Create a random-access file
6
7
8
RandomAccessFile inout =
new
RandomAccessFile(
"inout.dat"
,
"rw"
);
RandomAccessFile
// Clear the file to destroy the old contents, if any
9
10
11
inout.setLength(
0
);
empty file
// Write new integers to the file
12
for
(
int
i =
0
; i <
200
; i++)
13
14
15
// Display the current length of the file
16 System.out.println(
"Current file length is "
+
inout.writeInt(i);
write
inout.length()
);
17
18
// Retrieve the first number
19
// Move the file pointer to the beginning
20 System.out.println(
"The first number is "
+
inout.seek(
0
);
move pointer
read
inout.readInt()
);
21
22
// Retrieve the second number
23
// Move the file pointer to the second number
24 System.out.println(
"The second number is "
+
inout.seek(
1
*
4
);
inout.readInt()
);
25
26
// Retrieve the tenth number
27
// Move the file pointer to the tenth number
28 System.out.println(
"The tenth number is "
+
inout.seek(
9
*
4
);
inout.readInt()
);
29
30
// Modify the eleventh number
31
32
33
inout.writeInt(
555
);
// Append a new number
34
inout.seek(inout.length());
// Move the file pointer to the end
35
36
37
// Display the new length
38 System.out.println(
"The new length is "
+
inout.writeInt(
999
);
inout.length()
);
39
40
// Retrieve the new eleventh number
41
// Move the file pointer to the next number
42 System.out.println(
"The eleventh number is "
+
inout.seek(
10
*
4
);
inout.readInt()
);
43
44 inout.close();
45 }
46 }
close file
Current file length is 800
The first number is 0
The second number is 1
The tenth number is 9
The new length is 804
The eleventh number is 555
