@Override
    public Double parse(JsonParser jsonParser) throws IOException {
        if (jsonParser.getCurrentToken() == JsonToken.VALUE_NULL) {
            return null;
        } else {
            return jsonParser.getDoubleValue();
        }
    }
Built-in mapper for Double objects
core/src/main/java/com/bluelinelabs/logansquare/internal/objectmappers/DoubleMapper.java