GUID to ByteArray

Question

I just wrote this code to convert a GUID into a byte array. Can anyone shoot any holes in it or suggest something better?

 public static byte[] getGuidAsByteArray(){   UUID uuid = UUID.randomUUID();  long longOne = uuid.getMostSignificantBits();  long longTwo = uuid.getLeastSignificantBits();   return new byte[] {       (byte)(longOne >>> 56),       (byte)(longOne >>> 48),       (byte)(longOne >>> 40),       (byte)(longOne >>> 32),          (byte)(longOne >>> 24),       (byte)(longOne >>> 16),       (byte)(longOne >>> 8),       (byte) longOne,       (byte)(longTwo >>> 56),       (byte)(longTwo >>> 48),       (byte)(longTwo >>> 40),       (byte)(longTwo >>> 32),          (byte)(longTwo >>> 24),       (byte)(longTwo >>> 16),       (byte)(longTwo >>> 8),       (byte) longTwo        }; } 

In C++, I remember being able to do this, but I guess theres no way to do it in Java with the memory management and all?:

    UUID uuid = UUID.randomUUID();      long[] longArray = new long[2];     longArray[0] = uuid.getMostSignificantBits();     longArray[1] = uuid.getLeastSignificantBits();      byte[] byteArray = (byte[])longArray;     return byteArray; 

Edit

If you want to generate a completely random UUID as bytes that does not conform to any of the official types, this will work and wastes 10 fewer bits than type 4 UUIDs generated by UUID.randomUUID():

    public static byte[] getUuidAsBytes(){     int size = 16;     byte[] bytes = new byte[size];     new Random().nextBytes(bytes);     return bytes; } 

Answer 1

I would rely on built in functionality:

ByteBuffer bb = ByteBuffer.wrap(new byte[16]); bb.putLong(uuid.getMostSignificantBits()); bb.putLong(uuid.getLeastSignificantBits()); return bb.array(); 

or something like,

ByteArrayOutputStream ba = new ByteArrayOutputStream(16); DataOutputStream da = new DataOutputStream(ba); da.writeLong(uuid.getMostSignificantBits()); da.writeLong(uuid.getLeastSignificantBits()); return ba.toByteArray(); 

(Note, untested code!)

Answer 2

public static byte[] newUUID() {     UUID uuid = UUID.randomUUID();     long hi = uuid.getMostSignificantBits();     long lo = uuid.getLeastSignificantBits();     return ByteBuffer.allocate(16).putLong(hi).putLong(lo).array(); }