### Question:
NonNullValidator implements ConfijValidator<T> { public static <T> NonNullValidator<T> initiallyNotNull() { return new NonNullValidator<>(false); }  static NonNullValidator<T> initiallyNullable(); static NonNullValidator<T> initiallyNotNull(); @Override void validate(BindingResult<T> bindingResult);  }### Answer:
@Test void nullNotAllowedAsDefinedInBuilder() { assertThatThrownBy(() -> ConfijBuilder.of(WithNulls.class) .validateOnlyWith(NonNullValidator.initiallyNotNull()) .build()).hasMessageContaining("null") .hasMessageContaining(FIELD_NAME); }
@Test void okIfNotNullAsDefinedInBuilder() { String value = UUID.randomUUID() + ""; assertThat(ConfijBuilder.of(WithNulls.class) .validateOnlyWith(NonNullValidator.initiallyNotNull()) .loadFrom(ExplicitPropertiesSource.of(FIELD_NAME, value)) .build() .aField()).isEqualTo(value); }