### Question:
HashUtil { public static String rawChecksum(byte[] data) { return new String(getMessageDigest().digest(Preconditions.checkNotNull(data))); } private  HashUtil(); static String checksum(byte[] data); static String rawChecksum(byte[] data);  }### Answer:
@Test(expected = NullPointerException.class) public void testRawChecksumNPE() { HashUtil.rawChecksum(null); }
@Test public void testRawChecksum() throws Exception { assertNotNull(HashUtil.rawChecksum(new byte[]{})); assertNotNull(HashUtil.rawChecksum(new byte[]{Byte.MAX_VALUE, Byte.MIN_VALUE})); }