### Question:
SimpleKeyCryptoBuilder extends KeyCryptoBuilder { @Override public KeyCryptoBuilder setPrivateKey(final URI privateKey) { if (privateKey == null) { throw new NullPointerException("Private key location cannot be null."); } this.privateKey = privateKey; markAsSet(Attribute.PRIVATE_KEY); return this; }  @Override KeyCryptoProduct build(); @Override KeyCryptoBuilder setKeySalt(final String keySalt); @Override KeyCryptoBuilder setPrivateKey(final URI privateKey); @Override KeyCryptoBuilder setServerAddress(final URI serverAddress); @Override KeyCryptoBuilder setUsername(final String username);  }### Answer:
@Test(expected = NullPointerException.class) public void testNullPrivateKeyLocation() { builder.setPrivateKey(null); }