Static factory method Java 8 Collectors class

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Static factory method Collectors class

Factory Method	Return Type	For
toList	List<T>	The flow of all items collected in a List
Example of use: List <Dish> dishes = menuStream.collect (toList ());
toSet	Set<T>	The flow of all items collected to a Set, remove duplicates
Example of use: Set <Dish> dishes = menuStream.collect (toSet ());
toCollection	Collection<T>	The flow of all items collected to the collection given supply source created
使用示例： Collection<Dish> dishes = menuStream.collect(toCollection(),ArrayList::new);
counting	Long	Calculation of the number of elementary stream
Example of use: long howManyDishes = menuStream.collect (counting ());
summingInt	Integer	An integer convection in the project properties summing
Example of use: int totalCalories = menuStream.collect (summingInt (Dish :: getCalories));
averagingInt	Double	Integer property item average value calculated flow
Example of use: double avgCalories = menuStream.collect (averagingInt (Dish :: getCalories));
summarizingInt	IntSummaryStatistics	Collecting statistics on the attribute item Integer stream, such as maximum, minimum, sum and average
Example of use: IntSummaryStatistics menuStatistics = menuStream.collect (summarizingInt (Dish :: getCalories));
joining	String	Each item in the call connection convection generated string toString method
使用示例： String shortMenu = menuStream.map(Dish::getName).collect(joining(","));
maxBy	Optional<T>	Wrapped in a flow element according to a given maximum Optional comparator selected, or if the stream is empty compared Optional.empty ()
使用示例： Optional<Dish> fattest = menuStream.collect(maxBy(comparingInt(Dish::getCalories)));
minBy	Optional<T>	Optional smallest element of a package stream selected in accordance with the given comparator is empty, or if the stream was Optional.empty ()
使用示例： Optional<Dish> lightest = menuStream.collect(minBy(comparingInt(Dish::getCalories)));
reducing	Type reduction operations generated	As an initial value from an accumulator starts, one by one using BinaryOperator elements in conjunction with the flow, so as to flow together around a single value
使用示例： int totalCalories = menuStream.collect(reducing(0, Dish::getCalories, Integer::sum));
collectingAndThen	Type conversion function returns	Another wrapping accumulator, its result using the transform function
使用示例： int howManyDishes = menuStream.collect(collectingAndThen(toList(), List::size));
groupingBy	Map<K, List<T>>	根据项目的一个属性的值对流中的项目作问组，并将属性值作为结果 Map 的键
使用示例： Map<Dish.Type,List<Dish>> dishesByType = menuStream.collect(groupingBy(Dish::getType));
partitioningBy	Map<Boolean,List<T>>	根据对流中每个项目应用谓词的结果来对项目进行分区
使用示例： Map<Boolean,List<Dish>> vegetarianDishes = menuStream.collect(partitioningBy(Dish::isVegetarian));