Ok... have a look at this version. It doesn't work exactly (especially
if you increase the length of the BigInteger. I am not sure where
exactly the problem is. If you can fix it, post the version

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

public class BigNumber  {
       
   public static void main(String[] args) throws Exception       
  {
     FileWriter fstream = new FileWriter("number.txt");
     BufferedWriter fout = new BufferedWriter(fstream);
     PrintWriter out = new PrintWriter (fout);
               
      BigInteger bigInteger = new BigInteger (30,new Random());
     
      System.out.println(bigInteger);

      byte[] byteArray = bigInteger.toByteArray();
      int[] intArray = byteArrayToIntArray(byteArray, byteArray[0] <
0 ? -1 : 0);
     
      for (int  i : intArray)
      {
           System.out.println(i);
           out.print(i);
      }
      out.flush();
   }
   
/** Convert a big-endian byte array to a little-endian array of words.
*/  
   private static int[] byteArrayToIntArray(byte[] bytes, int sign)
  {
      // Determine number of words needed.
      int[] words = new int[bytes.length/4 + 1];
      int nwords = words.length;
 
     // Create a int out of modulo 4 high order bytes.
     int bptr = 0;
     int word = sign;
    for (int i = bytes.length % 4; i > 0; --i, bptr++)
             word = (word << 8) | (bytes[bptr] & 0xff);
    words[--nwords] = word;

    // Elements remaining in byte[] are a multiple of 4.
     while (nwords > 0)
      words[--nwords] = bytes[bptr++] << 24 |
             (bytes[bptr++] & 0xff) << 16 |
           (bytes[bptr++] & 0xff) << 8 |
           (bytes[bptr++] & 0xff);
    return words;
  }

            
}