Re: Reading from a Random Access File

christopher_board wrote:


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");
  }
}