See http://java.sun.com/docs/books/tutorial/essential/io/rafs.html

More Javaish would be

public class Employee {

Generally I find you don't need to prefix variable names with a type
indicator. This is because the Java compiler does a pretty good job of
preventing you from using the wrong data type in the wrong places.

PLEASE DON'T SHOUT! IT MAKES FOLK IRRITABLE!

Maybe you could use String.format() when writing it.
A lot of people seem to use .length() and add the required number of " "
to a String (or better to a StringBuffer or char[]).
All the above can be found by Googling for Java String pad.

You multiposted to c.l.j.p because you didn't get an answer here within
ten minutes. That sort of impatient behaviour may annoy lots of people
and make them less likely to help you.

I find this guide helpful in working out how to get answers in
newsgroups: http://www.catb.org/~esr/faqs/smart-questions.html

My advice is, if you don't know about the following, make an effort to
find out: Top-posting, multi-posting, quoting and trimming.

Good luck!

Java has java.io.RandomAccessFile.

Here is an example froma Mike Murach book:

import java.io.*;
import java.util.*;

public class BookIO{
private static Book book = null;
private static String[] codes = null;
private static RandomAccessFile randomFile = null;

private static final File BOOK_FILE = new File("books.dat");
private static final int CODE_SIZE = 4;
private static final int TITLE_SIZE = 20;
private static final int RECORD_SIZE = CODE_SIZE*2 + TITLE_SIZE*2 + 8;

public static void open() throws IOException{
 randomFile = new RandomAccessFile(BOOK_FILE, "rw");
 codes = readCodes();
}

public static void close(){
 try{
  randomFile.close();
 }
 catch(IOException e){
  System.out.println("I/OException thrown when closing file.");
 }
}

public static int getRecordCount() throws IOException{
 long length = BOOK_FILE.length();
 int recordCount = (int) (length / RECORD_SIZE);
 return recordCount;
}

public static String readString(DataInput in, int length)
throws IOException{
 String s = "";
 int i = 0;
 while (i < length){
  char c = in.readChar();
  if (c!=0)
   s += c;
  i++;
 }
 return s;
}

public static Book readRecord(int recordNumber) throws IOException{
 randomFile.seek((recordNumber-1) * RECORD_SIZE);
 String code = readString(randomFile, CODE_SIZE);
 String title = readString(randomFile, TITLE_SIZE);
 double price = randomFile.readDouble();
 book = new Book(code, title, price);
 return book;
}

public static Book readRecord(String bookCode) throws IOException{
 int recordNumber = getRecordNumber(bookCode);
 book = readRecord(recordNumber);
 return book;
}

public static int getRecordNumber(String bookCode) throws IOException{
 int match = -1;
 int i = 0;
 boolean flag = true;
 while ((i < getRecordCount()) && (flag==true)){
  if (bookCode.equals(codes[i])){
   match = i+1;
   flag = false;
  }
  i++;
 }
 return match;
}

public static String[] readCodes() throws IOException{
 codes = new String[getRecordCount()];
 for (int i = 0; i < getRecordCount(); i++){
  randomFile.seek(i * RECORD_SIZE);
  codes[i] = readString(randomFile, CODE_SIZE);
 }
 return codes;
}

public static String[] readTitles() throws IOException{
 String[] titles = new String[getRecordCount()];
 for (int i = 0; i < getRecordCount(); i++){
  randomFile.seek(i * RECORD_SIZE + 8);
  titles[i] = readString(randomFile, TITLE_SIZE);
 }
 return titles;
}

public static void writeString(DataOutput out, String s, int length)
throws IOException{
 for (int i = 0; i < length; i++){
  if (i < s.length())
   out.writeChar(s.charAt(i));
  else
   out.writeChar(0);
 }
}

public static void writeRecord(Book book, int recordNumber)
throws IOException{
 randomFile.seek((recordNumber-1) * RECORD_SIZE);
 writeString(randomFile, book.getCode(), CODE_SIZE);
 writeString(randomFile, book.getTitle(), TITLE_SIZE);
 randomFile.writeDouble(book.getPrice());
}

public static Book moveFirst() throws IOException{
 book = readRecord(1);
 return book;
}

public static Book movePrevious() throws IOException{
 //add code to handle if Prev button clicked on first record.
 int recordNumber = getRecordNumber(book.getCode());
 book = readRecord(recordNumber - 1);
 return book;
}

public static Book moveNext() throws IOException{
 //add code to handle if Next button clicked on last record.
 int recordNumber = getRecordNumber(book.getCode());
 book = readRecord(recordNumber + 1);
 return book;
}

public static Book moveLast() throws IOException{
 int lastRecordNumber = getRecordCount();
 book = readRecord(lastRecordNumber);
 return book;
}

public static void addRecord(Book addBook) throws IOException{
 writeRecord(addBook, getRecordCount() + 1);
 close();
 open();
}

public static void updateRecord(Book book) throws IOException{
 int recordNumber = getRecordNumber(book.getCode());
 //record needs to be written to file
}

public static void deleteRecord(String bookCode) throws IOException{
 int recordNumber = getRecordNumber(bookCode);
 Vector books = new Vector();
 for (int i = 0; i< getRecordCount(); i++){
  books.add(readRecord(i+1));
 }
 books.remove(recordNumber-1);
 randomFile.setLength(RECORD_SIZE *(getRecordCount() -1));
 for (int i = 0; i<books.size(); i++){
  writeRecord((Book)books.elementAt(i),i+1);
 }
 if (recordNumber < getRecordCount())
  book = readRecord(recordNumber);
 else
  book = readRecord(getRecordCount()-1);
 close();
 open();
}
}