anchor.diff:    public static final class DateSetDeserializer
       extends JsonDeserializer<Set<Date>>
     {
  +    @javax.annotation.Nonnull
       @Override
  -    public Set<Date> deserialize( final JsonParser parser, final DeserializationContext context )
  +    public Set<Date> deserialize( @javax.annotation.Nonnull final JsonParser parser, @javax.annotation.Nonnull final DeserializationContext context )
         throws IOException
       {
         return deserializeCollection( parser, context, Set.class, new HashSet<Date>() );
  
positive.code:     }
    }
  
    static Date parse( final DateFormat formatter, final String source )
      throws IOException
    {
      try
  
negative.code:     }
    }
  
    static void writeDates( @javax.annotation.Nonnull final Collection<Date> dates, @javax.annotation.Nonnull final JsonGenerator generator )
      throws IOException
    {
      final DateFormat formatter = newDateFormatter();
  