Simple UUIDv4 class in Java

UUIDv4.java

import java.util.BitSet;
import java.security.SecureRandom;

public class UUIDv4 {
    private static final boolean[] VERSION = new boolean[] {
            false, true, false, false // Version 4
    };

    private static final boolean[] VARIANT = new boolean[] {
            true, false // Variant
    };

    private final BitSet uuid = new BitSet(128);

    UUIDv4() {
        SecureRandom secRand = new SecureRandom();

        for (int j = 0; j < 128; j++) {
            if (j >= 48 && j < (52)) { // Set required version bits (v4)
                uuid.set(j, VERSION[j - 48]); continue;
            }

            if (j >= 64 && j < (66)) { // Set required variant bits
                uuid.set(j, VARIANT[j - 64]); continue;
            }

            uuid.set(j, secRand.nextBoolean()); // Generate UUID bit sequence
        }
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();

        for (int j = 0; j < 8; j++) {
            for (int k = 0; k < 4; k++) {

                int v = 0;

                for (int i = 0; i < 4; i++) {
                    int bit = ((j * 16) + (k * 4) + i);

                    if (uuid.get(bit)) {
                        v += (1 << (3 - i));
                    }

                    if (i == 3) {
                        sb.append((char) (
                                v < 10 ? '0' + v : 'a' + (v - 10)
                        ));
                    }

                    if (bit == 32 || bit == 48 || bit == 64 || bit == 80) {
                        sb.append("-");
                    }
                }
            }
        }

        return sb.toString();
    }
}