BINARY I/O - Introduction to Java Programming: Comprehensive Version - page 700

A RandomAccessFile is created for the file named inout.dat with mode rw to allow both
read and write operations in line 6.
inout.setLength(0) sets the length to 0 in line 9. This, in effect, destroys the old con-
tents of the file.
The for loop writes 200 int values from 0 to 199 into the file in lines 12 and 13. Since
each int value takes 4 bytes, the total length of the file returned from inout.length() is
now 800 (line 16), as shown in the sample output.
Invoking inout.seek(0) in line 19 sets the file pointer to the beginning of the file.
inout.readInt() reads the first value in line 20 and moves the file pointer to the next
number. The second number is read in line 24.
inout.seek(9 * 4) (line 27) moves the file pointer to the tenth number.
inout.readInt() reads the tenth number and moves the file pointer to the eleventh num-
ber in line 28. inout.write(555) writes a new eleventh number at the current position
(line 31). The previous eleventh number is destroyed.
inout.seek(inout.length()) moves the file pointer to the end of the file (line 34).
inout.writeInt(999) writes a 999 to the file (line 35). Now the length of the file is
increased by 4 , so inout.length() returns 804 (line 38).
inout.seek(10 * 4) moves the file pointer to the eleventh number in line 41. The new
eleventh number, 555 , is displayed in line 42.

17.31

✓ ✓

Can RandomAccessFile streams read and write a data file created by
DataOutputStream ? Can RandomAccessFile streams read and write objects?

Check

Point

17.32

Create a RandomAccessFile stream for the file address.dat to allow the updating
of student information in the file. Create a DataOutputStream for the file
address.dat . Explain the differences between these two statements.

17.33

What happens if the file test.dat does not exist when you attempt to compile and run
the following code?

import java.io.*;

public class Test {
public static void main(String[] args) {
try ( RandomAccessFile raf =
new RandomAccessFile( "test.dat" , "r" ); ) {
int i = raf.readInt();

}
catch (IOException ex) {
System.out.println( "IO exception" );
}
}
}

K EY T ERMS

binary I/O 678
deserialization 695
file pointer 698
random-access file

sequential-access file 697

serialization 695

stream 678

697 text I/O 678