我将列表对象转换为映射字符串,列表对象时遇到问题.我正在寻找具有汽车中所有组件的键名称的Map,并且值由具有该组件的汽车表示
public class Car {
private String model;
private List<String> components;
// getters and setters
}
public Map<String,List<Car>> componentsInCar() {
HashSet<String> components = new HashSet<>();
cars.stream().forEach(x -> x.getComponents().stream().forEachOrdered(components::add));
Map<String,List<Car>> mapCarsComponents = new HashMap<>();
for (String keys : components) {
mapCarsComponents.put(keys,cars.stream().filter(c -> c.getComponents().contains(keys)).collect(Collectors.toList()));
}
return mapCarsComponents;
}
最佳答案
您也可以使用流来做到这一点,但是我发现这更具可读性：
public static Map<String,List<Car>> componentsInCar(List<Car> cars) {
Map<String,List<Car>> result = new HashMap<>();
cars.forEach(car -> {
car.getComponents().forEach(comp -> {
result.computeIfAbsent(comp,ignoreMe -> new ArrayList<>()).add(car);
});
});
return result;
}
或使用流：
public static Map<String,List<Car>> componentsInCar(List<Car> cars) {
return cars.stream()
.flatMap(car -> car.getComponents().stream().distinct().map(comp -> new SimpleEntry<>(comp,car)))
.collect(Collectors.groupingBy(
Entry::getKey,Collectors.mapping(Entry::getValue,Collectors.toList())
));
}
