Going back and forth between BitSet and redis bit sets in Java

SieveOfEratosthenes.java

import java.util.BitSet;

import redis.clients.jedis.Jedis;

public class SieveOfEratosthenes {

    private static String sieveSetKeyCorrected = "correct_sieve";
    private static String sieveSetKeyDefaultJava = "wrong_sieve";
    private static String spoolSieve = "sieve_set_bits";

    /**
     * @param args
     */
    public static void main(final String[] args) {

        // Initialize my redis client values
        final Jedis redis = new Jedis("localhost");

        System.out.println("Alright, let's create a sieve of primes, Eratosthenes style!");
        final int length = 20;
        final BitSet primes = new BitSet(length);
        primes.flip(2, length);
        for (int i = 0; i < length; i++) {
            if (primes.get(i)) {
                for (int j = i * 2; j < length; j += i) {
                    primes.set(j, false);
                }
            }
        }

        System.out.println("Let's set the bits in redis the ol' fashioned way");
        System.out.println("One at a time using redis.setbit");
        for (int i = 0; i < primes.length(); i++) {
            if (primes.get(i)) {
                redis.setbit(spoolSieve, i, true);
            }
        }

        System.out.println("And then read the bitset out, just like the example");
        final BitSet spoolWaySieve = BitSet.valueOf(redis.get(spoolSieve.getBytes()));

        System.out.println("And compare the values");
        System.out.println("Original Sieve: " + primes);
        System.out.println("Read via BitSet.valueOf(): " + spoolWaySieve);

        System.out.println("\nWhat The? Thats not right at all!");
        System.out.println("Let's try reversing the bits in the bytes");

        final BitSet correctedBits = fromByteArrayReverse(redis.get(spoolSieve.getBytes()));

        System.out.println("And compare the values");
        System.out.println("Original Sieve: " + primes);
        System.out.println("Read via helper method: " + correctedBits);

        System.out.println("\nThat's better.");
        System.out.println("Now what happens if I try to write the entire BitSet into Redis");
        System.out.println("Using the BitSet.toByteArray() method built-in");
        System.out.println("Then pull the values back out");

        redis.set(sieveSetKeyDefaultJava.getBytes(), primes.toByteArray());
        final BitSet defaultJava =
            BitSet.valueOf(redis.get(sieveSetKeyDefaultJava.getBytes()));
        System.out.println("Original Sieve: " + primes);
        System.out
            .println("Stored via BitSet.toByteArray() and retrieved via BitSet.valueOf: "
                + defaultJava);

        System.out.println("\nThat appears to work...but there is a catch");
        System.out.println("If you try to read the values out using getBit");
        System.out
            .println("They are mangled because we effectively used Java's byte ordering");
        System.out.println("Look. redis.getbit(4) -> "
            + redis.getbit(sieveSetKeyDefaultJava, 4));
        System.out.println("Last I checked, 4 is not prime");
        System.out.println("\nThis also means calls to getbit from another language");
        System.out.println("and especially redis-cli, will be incorrect");

        System.out
            .println("\nSo, let's write another helper method to reverse the bits on the way in");
        System.out.println("And write the sieve of primes");
        System.out.println("And check to make sure the native calls to getBit still work");
        System.out.println("And use our helper method to get the BitSet in one call");

        redis.set(sieveSetKeyCorrected.getBytes(), toByteArrayReverse(primes));
        final BitSet correctedSieve =
            fromByteArrayReverse(redis.get(sieveSetKeyCorrected.getBytes()));

        System.out.println("Original Sieve: " + primes);
        System.out.println("Stored via helper method and retrieved via helper method: "
            + correctedSieve);
        System.out
            .println("Look. redis.getbit(4) -> " + redis.getbit(sieveSetKeyCorrected, 4));

        System.out
            .println("\nThere we go. Use a help method to reverse the bits on the way in or out");
        System.out.println("To make sure your native calls still work");
    }

    public static BitSet fromByteArrayReverse(final byte[] bytes) {
        final BitSet bits = new BitSet();
        for (int i = 0; i < bytes.length * 8; i++) {
            if ((bytes[i / 8] & (1 << (7 - (i % 8)))) != 0) {
                bits.set(i);
            }
        }
        return bits;
    }

    public static byte[] toByteArrayReverse(final BitSet bits) {
        final byte[] bytes = new byte[bits.length() / 8 + 1];
        for (int i = 0; i < bits.length(); i++) {
            if (bits.get(i)) {
                final int value = bytes[i / 8] | (1 << (7 - (i % 8)));
                bytes[i / 8] = (byte) value;
            }
        }
        return bytes;
    }
}

final BitSet correctedBits = fromByteArrayReverse(redis.get(spoolSieve.getBytes()));
Why did you convert the redis key from string to byte[] ?