<p>I have the following fields:</p>

<ul>
<li>Inventory control (16 byte record)

<ul>
<li>Product ID code (int – 4 bytes)</li>
<li>Quantity in stock (int – 4 bytes)</li>
<li>Price (double – 8 bytes)</li>
</ul></li>
</ul>

<p>How do I create a fixed length random access file using the above lengths? I tried some examples online, but I either get an EOF exception or random address values when I try to access them.</p>

<p>I tried some more examples and couldn't understand the concept very well. I'm trying a project with it and will try to explore more on it.</p>

<p>Here is some example data. There might be holes in the data where <code>No. in stock</code> could be <code>23 == 023</code>.</p>

<pre><code>          Quantity
ID. No.   In Stock   Price

-------   --------   ------
 1001       476      $28.35
 1002       240      $32.56
 1003       517      $51.27
 1004       284      $23.75
 1005       165      $32.25
</code></pre>

<p>Thanks for the help.</p>

java.io.RandomAccessFile is the class you're looking for. Here's an example implementation (you'll probably want to write some unit tests, as I haven't :)
```
```
package test;

import java.io.IOException;
import java.io.RandomAccessFile;

public class Raf {
    private static class Record{
        private final double price;
        private final int id;
        private final int stock;

        public Record(int id, int stock, double price){
            this.id = id;
            this.stock = stock;
            this.price = price;
        }

        public void pack(int n, int offset, byte[] array){
            array[offset + 0] = (byte)(n & 0xff);
            array[offset + 1] = (byte)((n >> 8) & 0xff);
            array[offset + 2] = (byte)((n >> 16) & 0xff);
            array[offset + 3] = (byte)((n >> 24) & 0xff);
        }

        public void pack(double n, int offset, byte[] array){
            long bytes = Double.doubleToRawLongBits(n);
            pack((int) (bytes & 0xffffffff), offset, array);
            pack((int) ((bytes >> 32) & 0xffffffff), offset + 4, array);
        }

        public byte[] getBytes() {
            byte[] record = new byte[16];
            pack(id, 0, record);
            pack(stock, 4, record);
            pack(price, 8, record);
            return record;
        }
    }

    private static final int RECORD_SIZE = 16;
    private static final int N_RECORDS = 1024;

    /**
     * @param args
     * @throws IOException 
     */
    public static void main(String[] args) throws IOException {
        RandomAccessFile raf = new RandomAccessFile(args[0], "rw");
        try{
            raf.seek(RECORD_SIZE * N_RECORDS);

            raf.seek(0);

            raf.write(new Record(1001, 476, 28.35).getBytes());
            raf.write(new Record(1002, 240, 32.56).getBytes());
        } finally {
            raf.close();
        }
    }
}
```
```