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java.util.stream.Collectors
| 修饰符和类型 | 方法 | 描述 |
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static <T>?Collector<T,??,?Double> | averagingDouble?(ToDoubleFunction<? super T>?mapper) | 返回求输入Double类型元素平均值的Collector |
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static <T>?Collector<T,??,?Double> | averagingInt?(ToIntFunction<? super T>?mapper) | 返回求输入Interger类型元素平均值的Collector |
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static <T>?Collector<T,??,?Double> | averagingLong?(ToLongFunction<? super T>?mapper) | 返回求输入Long类型元素平均值的Collector |
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static <T,?A,?R,?RR>
Collector<T,?A,?RR> | collectingAndThen?(Collector<T,?A,?R>?downstream,?Function<R,?RR>?finisher) | 调整收集器在完成收集后应用额外的转换逻辑 |
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static <T>?Collector<T,??,?Long> | counting() | 返回一个接受T类型元素的Collector，用于统计T元素的个数 |
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static <T,?A,?R>
Collector<T,??,?R> | filtering?(Predicate<? super T>?predicate,?Collector<? super T,?A,?R>?downstream) | 通过对每个输入元素应用Predicate，使收集器适应于一个接受相同类型T的元素，并只在Predicate返回true时进行累积。 ? |
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static <T,?U,?A,?R>
Collector<T,??,?R> | flatMapping?(Function<? super T,?? extends?Stream<? extends U>>?mapper,Collector<? super U,?A,?R>?downstream) | 通过在累积之前对每个输入元素应用Function映射函数，将一个接受U类型元素的收集器调整为一个接受T类型元素。 ? |
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static <T,?K>
Collector<T,??,?Map<K,?List<T>>> | groupingBy?(Function<? super T,?? extends K>?classifier) | Returns a?Collector?implementing a "group by" operation on input elements of type?T, grouping elements according to a classification function, and returning the results in a?Map. |
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static <T,?K,?D,?A,?M extendsMap<K,?D>>
Collector<T,??,?M> | groupingBy?(Function<? super T,?? extends K>?classifier,Supplier<M>?mapFactory,?Collector<? super T,?A,?D>?downstream) | Returns a?Collector?implementing a cascaded "group by" operation on input elements of type?T, grouping elements according to a classification function, and then performing a reduction operation on the values associated with a given key using the specified downstream?Collector. |
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static <T,?K,?A,?D>
Collector<T,??,?Map<K,?D>> | groupingBy?(Function<? super T,?? extends K>?classifier,?Collector<? super T,?A,?D>?downstream) | Returns a?Collector?implementing a cascaded "group by" operation on input elements of type?T, grouping elements according to a classification function, and then performing a reduction operation on the values associated with a given key using the specified downstream?Collector. |
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static <T,?K>
Collector<T,??,?ConcurrentMap<K,?List<T>>> | groupingByConcurrent?(Function<? super T,?? extends K>?classifier) | Returns a concurrent?Collector?implementing a "group by" operation on input elements of type?T, grouping elements according to a classification function. |
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static <T,?K,?A,?D,?M extendsConcurrentMap<K,?D>>
Collector<T,??,?M> | groupingByConcurrent?(Function<? super T,?? extends K>?classifier,Supplier<M>?mapFactory,?Collector<? super T,?A,?D>?downstream) | Returns a concurrent?Collector?implementing a cascaded "group by" operation on input elements of type?T, grouping elements according to a classification function, and then performing a reduction operation on the values associated with a given key using the specified downstream?Collector. |
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static <T,?K,?A,?D>
Collector<T,??,?ConcurrentMap<K,?D>> | groupingByConcurrent?(Function<? super T,?? extends K>?classifier,Collector<? super T,?A,?D>?downstream) | Returns a concurrent?Collector?implementing a cascaded "group by" operation on input elements of type?T, grouping elements according to a classification function, and then performing a reduction operation on the values associated with a given key using the specified downstream?Collector. |
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staticCollector<CharSequence,??,?String> | joining() | Returns a?Collector?that concatenates the input elements into a?String, in encounter order. |
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staticCollector<CharSequence,??,?String> | joining?(CharSequence?delimiter) | Returns a?Collector?that concatenates the input elements, separated by the specified delimiter, in encounter order. |
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staticCollector<CharSequence,??,?String> | joining?(CharSequence?delimiter,?CharSequence?prefix,CharSequence?suffix) | Returns a?Collector?that concatenates the input elements, separated by the specified delimiter, with the specified prefix and suffix, in encounter order. |
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static <T,?U,?A,?R>
Collector<T,??,?R> | mapping?(Function<? super T,?? extends U>?mapper,?Collector<? super U,?A,?R>?downstream) | Adapts a?Collector?accepting elements of type?U?to one accepting elements of type?T?by applying a mapping function to each input element before accumulation. |
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static <T>?Collector<T,??,?Optional<T>> | maxBy?(Comparator<? super T>?comparator) | Returns a?Collector?that produces the maximal element according to a given?Comparator, described as an?Optional<T>. |
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static <T>?Collector<T,??,?Optional<T>> | minBy?(Comparator<? super T>?comparator) | Returns a?Collector?that produces the minimal element according to a given?Comparator, described as an?Optional<T>. |
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static <T>?Collector<T,??,?Map<Boolean,?List<T>>> | partitioningBy?(Predicate<? super T>?predicate) | Returns a?Collector?which partitions the input elements according to a?Predicate, and organizes them into a?Map<Boolean, List<T>>. |
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static <T,?D,?A>
Collector<T,??,?Map<Boolean,?D>> | partitioningBy?(Predicate<? super T>?predicate,?Collector<? super T,?A,?D>?downstream) | Returns a?Collector?which partitions the input elements according to a?Predicate, reduces the values in each partition according to another?Collector, and organizes them into a?Map<Boolean, D>?whose values are the result of the downstream reduction. |
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static <T>?Collector<T,??,?Optional<T>> | reducing?(BinaryOperator<T>?op) | Returns a?Collector?which performs a reduction of its input elements under a specified?BinaryOperator. |
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static <T>?Collector<T,??,?T> | reducing?(T?identity,?BinaryOperator<T>?op) | Returns a?Collector?which performs a reduction of its input elements under a specified?BinaryOperator?using the provided identity. |
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static <T,?U>
Collector<T,??,?U> | reducing?(U?identity,?Function<? super T,?? extends U>?mapper,BinaryOperator<U>?op) | Returns a?Collector?which performs a reduction of its input elements under a specified mapping function and?BinaryOperator. |
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static <T>?Collector<T,??,?DoubleSummaryStatistics> | summarizingDouble?(ToDoubleFunction<? super T>?mapper) | Returns a?Collector?which applies an?double-producing mapping function to each input element, and returns summary statistics for the resulting values. |
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static <T>?Collector<T,??,?IntSummaryStatistics> | summarizingInt?(ToIntFunction<? super T>?mapper) | Returns a?Collector?which applies an?int-producing mapping function to each input element, and returns summary statistics for the resulting values. |
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static <T>?Collector<T,??,?LongSummaryStatistics> | summarizingLong?(ToLongFunction<? super T>?mapper) | Returns a?Collector?which applies an?long-producing mapping function to each input element, and returns summary statistics for the resulting values. |
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static <T>?Collector<T,??,?Double> | summingDouble?(ToDoubleFunction<? super T>?mapper) | Returns a?Collector?that produces the sum of a double-valued function applied to the input elements. |
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static <T>?Collector<T,??,?Integer> | summingInt?(ToIntFunction<? super T>?mapper) | Returns a?Collector?that produces the sum of a integer-valued function applied to the input elements. |
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static <T>?Collector<T,??,?Long> | summingLong?(ToLongFunction<? super T>?mapper) | Returns a?Collector?that produces the sum of a long-valued function applied to the input elements. |
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static <T,?C extendsCollection<T>>
Collector<T,??,?C> | toCollection?(Supplier<C>?collectionFactory) | Returns a?Collector?that accumulates the input elements into a new?Collection, in encounter order. |
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static <T,?K,?U>
Collector<T,??,?ConcurrentMap<K,?U>> | toConcurrentMap?(Function<? super T,?? extends K>?keyMapper,?Function<? super T,?? extends U>?valueMapper) | Returns a concurrent?Collector?that accumulates elements into a?ConcurrentMap?whose keys and values are the result of applying the provided mapping functions to the input elements. |
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static <T,?K,?U>
Collector<T,??,?ConcurrentMap<K,?U>> | toConcurrentMap?(Function<? super T,?? extends K>?keyMapper,?Function<? super T,?? extends U>?valueMapper,?BinaryOperator<U>?mergeFunction) | Returns a concurrent?Collector?that accumulates elements into a?ConcurrentMap?whose keys and values are the result of applying the provided mapping functions to the input elements. |
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static <T,?K,?U,?M extendsConcurrentMap<K,?U>>
Collector<T,??,?M> | toConcurrentMap?(Function<? super T,?? extends K>?keyMapper,?Function<? super T,?? extends U>?valueMapper,?BinaryOperator<U>?mergeFunction,Supplier<M>?mapFactory) | Returns a concurrent?Collector?that accumulates elements into a?ConcurrentMap?whose keys and values are the result of applying the provided mapping functions to the input elements. |
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static <T>?Collector<T,??,?List<T>> | toList() | Returns a?Collector?that accumulates the input elements into a new?List. |
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static <T,?K,?U>
Collector<T,??,?Map<K,?U>> | toMap?(Function<? super T,?? extends K>?keyMapper,?Function<? super T,?? extends U>?valueMapper) | Returns a?Collector?that accumulates elements into a?Map?whose keys and values are the result of applying the provided mapping functions to the input elements. |
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static <T,?K,?U>
Collector<T,??,?Map<K,?U>> | toMap?(Function<? super T,?? extends K>?keyMapper,?Function<? super T,?? extends U>?valueMapper,?BinaryOperator<U>?mergeFunction) | Returns a?Collector?that accumulates elements into a?Map?whose keys and values are the result of applying the provided mapping functions to the input elements. |
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static <T,?K,?U,?M extendsMap<K,?U>>
Collector<T,??,?M> | toMap?(Function<? super T,?? extends K>?keyMapper,?Function<? super T,?? extends U>?valueMapper,?BinaryOperator<U>?mergeFunction,Supplier<M>?mapFactory) | Returns a?Collector?that accumulates elements into a?Map?whose keys and values are the result of applying the provided mapping functions to the input elements. |
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static <T>?Collector<T,??,?Set<T>> | toSet() | Returns a?Collector?that accumulates the input elements into a new?Set. |
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static <T>?Collector<T,??,?List<T>> | toUnmodifiableList() | Returns a?Collector?that accumulates the input elements into an?unmodifiable List?in encounter order. |
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static <T,?K,?U>
Collector<T,??,?Map<K,?U>> | toUnmodifiableMap?(Function<? super T,?? extends K>?keyMapper,?Function<? super T,?? extends U>?valueMapper) | Returns a?Collector?that accumulates the input elements into an?unmodifiable Map, whose keys and values are the result of applying the provided mapping functions to the input elements. |
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static <T,?K,?U>
Collector<T,??,?Map<K,?U>> | toUnmodifiableMap?(Function<? super T,?? extends K>?keyMapper,?Function<? super T,?? extends U>?valueMapper,?BinaryOperator<U>?mergeFunction) | Returns a?Collector?that accumulates the input elements into an?unmodifiable Map, whose keys and values are the result of applying the provided mapping functions to the input elements. |
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static <T>?Collector<T,??,?Set<T>> | toUnmodifiableSet() | Returns a?Collector?that accumulates the input elements into an?unmodifiable Set. |
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