File I/O - Absolute Java - page 636

Display 10.22 Random Access to a File (part 1 of 2)

1 import java.io.RandomAccessFile;
2 import java.io.IOException;
3 import java.io.FileNotFoundException;

4 public class RandomAccessDemo
5 {
6 public static void main(String[] args)
7 {
8 try
9 {
10 RandomAccessFile ioStream =
11 new RandomAccessFile("bytedata", "rw");

12 System.out.println("Writing 3 bytes to the file bytedata.");
13 ioStream.writeByte(1);
14 ioStream.writeByte(2);
15 ioStream.writeByte(3);
16 System.out.println("The length of the file is now = "
17 + ioStream.length());
18 System.out.println("The file pointer location is "
19 + ioStream.getFilePointer());

20 System.out.println("Moving the file pointer to location 1.");
21 ioStream.seek(1);
22 byte oneByte = ioStream.readByte();
23 System.out.println("The value at location 1 is " + oneByte);
24 oneByte = ioStream.readByte();
25 System.out.println("The value at the next location is "
26 + oneByte);

27 System.out.println("Now we move the file pointer back to");
28 System.out.println("location 1, and change the byte.");
29 ioStream.seek(1);
30 ioStream.writeByte(9);
31 ioStream.seek(1);
32 oneByte = ioStream.readByte();
33 System.out.println("The value at location 1 is now "
+ oneByte);

34 System.out.println("Now we go to the end of the file");
35 System.out.println("and write a double.");
36 ioStream.seek(ioStream.length());
37 ioStream.writeDouble(41.99);
38 System.out.println("The length of the file is now = "
39 + ioStream.length());