anchor.diff:    public static final class DateSetDeserializer
       extends JsonDeserializer<Set<Date>>
     {
  -    @javax.annotation.Nonnull
       @Override
  -    public Set<Date> deserialize( @javax.annotation.Nonnull final JsonParser parser, @javax.annotation.Nonnull final DeserializationContext context )
  +    public Set<Date> deserialize( final JsonParser parser, final DeserializationContext context )
         throws IOException
       {
         return deserializeCollection( parser, context, Set.class, new HashSet<Date>() );
  
positive.code:     extends JsonSerializer<Set<Date>>
    {
      @Override
      public void serialize( @javax.annotation.Nonnull final Set<Date> dates,
                             @javax.annotation.Nonnull final JsonGenerator generator,
                             @javax.annotation.Nonnull final SerializerProvider provider )
        throws IOException
      {
        generator.writeStartArray();
  
negative.code:     extends JsonSerializer<Date>
    {
      @Override
      public void serialize( final Date date,
                             final JsonGenerator generator,
                             final SerializerProvider provider )
        throws IOException
      {
        generator.writeString( newDateFormatter().format( date ) );
  