### Question:
Hash { public static byte[] sha256(final byte[]... data) { return digests.get().digest(Bytes.concat(data)); }  static byte[] sha256(final byte[]... data);  }### Answer:
@Test public void multiple256() { TestUtil.assertHex( "936a185caaa266bb9cbe981e9e05cb78cd732b0b3280eb944412bb6f8f8f07af", Hash.sha256("hello".getBytes(), "world".getBytes())); }
@Test public void single256() { TestUtil.assertHex( "2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824", Hash.sha256("hello".getBytes())); }
@Test public void empty256() { TestUtil.assertHex( "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855", Hash.sha256()); }
@Test(expected = NullPointerException.class) public void null256() { Hash.sha256(null); }