我有一种方法可以为从API请求调用中接收到的对象列表计算营养素。
该方法如下所示:
public Nutrients nutrientsCalculator(DailyMeals dailyMeals) {
String foodNamesForRequest = prepareFoodNamesForRequest(dailyMeals);
HttpEntity<NutrientsBodyForRequest> requestBody = prepareRequestForAPICall(foodNamesForRequest);
ResponseEntity<List<FoodNutritional>> response =
//create request here
if (nonNull(response.getBody())) {
double totalFat = response.getBody()
.stream()
.map(FoodNutritional::getTotalFat)
.mapToDouble(Double::doubleValue)
.sum();
double totalProtein = response.getBody()
.stream()
.map(FoodNutritional::getProtein)
.mapToDouble(Double::doubleValue)
.sum();
double totalCarbohydrates = response.getBody()
.stream()
.map(FoodNutritional::getTotalCarbohydrate)
.mapToDouble(Double::doubleValue)
.sum();
double totalDietaryFiber = response.getBody()
.stream()
.map(FoodNutritional::getDietaryFiber)
.mapToDouble(Double::doubleValue)
.sum();
return Nutrients.builder()
.carbohydrates(totalCarbohydrates)
.protein(totalProtein)
.fat(totalFat)
.dietaryFiber(totalDietaryFiber)
.build();
}
return new Nutrients();
}
我的FoodNutritional.class看起来像:
@JsonInclude(JsonInclude.Include.NON_NULL)
@JsonIgnoreProperties(ignoreUnknown = true)
@Getter
@Setter
@Builder
@NoArgsConstructor
@AllArgsConstructor
@EqualsAndHashCode
class FoodNutritional {
@JsonProperty("food_name")
private String foodName;
@JsonProperty("brand_name")
private String brandName;
@JsonProperty("serving_qty")
private Integer servingQuantity;
@JsonProperty("serving_unit")
private String servingUnit;
@JsonProperty("serving_weight_grams")
private String servingWeightGrams;
@JsonProperty("nf_calories")
private Double calories;
@JsonProperty("nf_total_fat")
private Double totalFat;
@JsonProperty("nf_saturated_fat")
private Double saturatedFat;
@JsonProperty("nf_cholesterol")
private Double cholesterol;
@JsonProperty("nf_sodium")
private Double sodium;
@JsonProperty("nf_total_carbohydrate")
private Double totalCarbohydrate;
@JsonProperty("nf_dietary_fiber")
private Double dietaryFiber;
@JsonProperty("nf_sugars")
private Double sugars;
@JsonProperty("nf_protein")
private Double protein;
@JsonProperty("nf_potassium")
private Double potassium;
}
我的方法解决方案可行,但我开始考虑是否有可能摆脱这种
sum
流方法样板。我要实现的是对单个字段求和:
totalFat
,protein
,dietaryFiber
,totalCarbohydrate
并将它们作为新对象的组件字段返回。我将很高兴为您提供有关如何提高当前版本代码质量的建议。
编辑:
在周末,我花了一点时间找到了另一种可以满足要求且功能更多的附加方法。最后,我创建了两个静态方法,例如:
private static Nutrients reduceNutrients(Nutrients n1, Nutrients n2) {
return Nutrients.builder()
.protein(n1.getProtein() + n2.getProtein())
.carbohydrates(n1.getCarbohydrates() + n2.getCarbohydrates())
.dietaryFiber(n1.getDietaryFiber() + n2.getDietaryFiber())
.fat(n1.getFat() + n2.getFat())
.build();
}
private static Nutrients fromFoodNutritionalToNutrients(FoodNutritional foodNutritional) {
return Nutrients.builder()
.dietaryFiber(foodNutritional.getDietaryFiber())
.carbohydrates(foodNutritional.getTotalCarbohydrate())
.fat(foodNutritional.getTotalFat())
.protein(foodNutritional.getProtein())
.build();
}
毕竟我像这样使用它:
Stream<FoodNutritional> foodNutritionalStream = Optional.ofNullable(response.getBody()).stream()
.flatMap(List::stream);
Nutrients nutrients = foodNutritionalStream
.map(NutrientsCalculatorService::fromFoodNutritionalToNutrients)
.reduce(NutrientsCalculatorService::reduceNutrients)
.orElseThrow(() -> new CustomException("custom_exception");
尽管如此,对
@Koziołek
,@Nir Levy
和@Naman
的问候仍然是我的缪斯。感谢您的每一个 promise 。
最佳答案
让我们介绍NutritionAccumulator
类:
class NutritionAccumulator{
private double fat = 0.;
private double carbs = 0.;
private double fiber = 0.;
private double protein = 0.;
public NutritionAccumulator() {
}
public NutritionAccumulator(double fat, double carbs, double fiber, double protein) {
this.fat = fat;
this.carbs = carbs;
this.fiber = fiber;
this.protein = protein;
}
public NutritionAccumulator add(NutritionAccumulator that){
return new NutritionAccumulator(this.fat + that.fat,
this.carbs + that.carbs,
this.fiber + that.fiber,
this.protein + that.protein
);
}
}
现在我们可以编写简单的stream reduce:
Optional.ofNullable(response.body())
.stream()
.reduce(
new NutritionAccumulator(),
(acc, fudNut) -> new NutritionAccumulator(
fudNut.getTotalFat(),
fudNut.getTotalCarbohydrate(),
fudNut.getDietaryFiber(),
fudNut.getProtein()
).add(acc),
NutritionAccumulator::add
);
最后,您可以将结果从上方传递给生成器。
关于java - 如何汇总对象列表的各个字段并以单个对象的形式返回结果,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/58337209/