uuid ranges in Java using BigInteger

gistfile1.java

import java.math.BigInteger;

public class TryBigInt {

    public static void main(String[] args) {
        BigInteger start = new BigInteger("00000000000000000000000000000000", 16);
        BigInteger end = new BigInteger("ffffffffffffffffffffffffffffffff", 16);
        final long numRanges = 11;
        BigInteger jump = (end.subtract(start)).divide(BigInteger.valueOf(numRanges));

        for (long ii = 0; ii < numRanges; ii++) {
            final BigInteger rangeStart = jump.multiply(BigInteger.valueOf(ii));
            final BigInteger rangeEnd;
            if (ii < numRanges - 1) {
                rangeEnd = rangeStart.add(jump);
            } else {
                rangeEnd = end;
            }
            System.out.println(ii + " " + rangeStart.toString(16) + " to " + rangeEnd.toString(16) + " (size = " + String.format("%01.03e", rangeEnd.subtract(rangeStart).doubleValue()) + ")");

            // to byte array
            byte[] bytesStart = toBytes(rangeStart);
            byte[] bytesEnd = toBytes(rangeEnd);

            System.out.format("%s -> %s\n", hex(bytesStart), hex(bytesEnd));
        }
    }

    private static String hex(byte[] bytes) {
        StringBuilder sb = new StringBuilder();
        for (byte b: bytes) {
            sb.append(String.format("%02x", b & 0xff));
        }
        return sb.toString();
    }

    private static byte[] toBytes(BigInteger x) {
        byte[] bytes = x.toByteArray();
        if (bytes.length == 16) {
            return bytes;
        }

        // copy least significant 16 bytes
        byte[] ret = new byte[16];
        for (int ii=0; ii<bytes.length && ii<ret.length; ii++) {
            ret[ret.length-1-ii] = bytes[bytes.length-1-ii];
        }

        return ret;
    }
}