Re: Reading from a Random Access File


christopher_board wrote:
Hi and thanks for your help. I used the code that you provided me and
it comes up with the following output messages. I have changed the
system.out a little to make it clear for me what information was being
outputted to the screen.

This is what got outputted when I ran the program

the length of the file6

the file pointer is located at 0

the file pointer is now located at 2

the first byte read is: 6

the file pointer has now been moved to 3

the file pointer has been moved 6

The read error is: java.io.EOFException


Thanks for your help in this matter


OK, although I'm still not sure what you're attempting.
Perhaps this is closer to what you're looking for.

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.io.RandomAccessFile;

public class finalTest
{
public static void main(String[] args)
{
writeData();
readData();
}

/**
* Since you haven't shown us the contents of your file, I'll make one up
here.
* It consists of lines of characters. Each line starts with a character
* representation of an integer, which represents the room number.
Followed by
* a space character used as a field delimiter. Followed by a character
* representation of an integer which represents the number of computers
in
* the room. Followed by a newline character(s), used as a record
delimiter.
* (Platform dependant.)
*/
public static void writeData()
{
File f = new File("Class Room Details.rsh");
try
{
FileWriter fw = new FileWriter(f);
int[] roomNumber = new int[]
{ 101, 102, 103, 104, 105 };
int[] computerCount = new int[]
{ 1, 2, 3, 4, 5 };
StringBuilder fileContents = new StringBuilder();
for (int loopIndex = 0; loopIndex < roomNumber.length; loopIndex++)
{
fileContents.append(roomNumber[loopIndex]);
fileContents.append(" ");
fileContents.append(computerCount[loopIndex]);
fileContents.append("\n");
}
fw.write(fileContents.toString());
fw.close();
}
catch (FileNotFoundException e)
{
e.printStackTrace();
}
catch (IOException e)
{
e.printStackTrace();
}
}

/**
* I haven't understood why you insist on a RandomAccessFile and using
* readByte() and skipByte() so I didn't attempt to use them here,
especially
* since you haven't provided a clue as to what your file format is.
*/
public static void readData()
{
String dataLine = null;
int roomNumber;
int computerCount;
try
{
File f = new File("Class Room Details.rsh");
RandomAccessFile raf = new RandomAccessFile(f, "r");
System.out.println("The length of the file is: " + raf.length()
+ " bytes.");
System.out.println("the file pointer is located at: "
+ raf.getFilePointer());
while (raf.getFilePointer() < raf.length())
{
dataLine = raf.readLine();
String[] data = dataLine.split(" ");
roomNumber = Integer.valueOf(data[0]);
computerCount = Integer.valueOf(data[1]);
shutdownComputers(roomNumber, computerCount);
}
raf.close();
}
catch (IOException e)
{
e.printStackTrace();
}
}

static void shutdownComputers(int room, int count)
{
System.out.println("Shutdown " + count + " computers in Room " + room
+ ". Bye");
}
}


.

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