Package com.tangosol.util.stream

Class RemoteCollectors

java.lang.Object
com.tangosol.util.stream.RemoteCollectors
public abstract class RemoteCollectors extends Object
Static factory for various RemoteCollectors that can be executed in parallel in a distributed environment.
Since:
12.2.1
Author:
as 2014.10.01
See Also:

  • Constructor Details

    • RemoteCollectors

      public RemoteCollectors()

  • Method Details

    • toCollection

      public static <T, C extends Collection<T>> RemoteCollector<T,?,C> toCollection(Remote.Supplier<C> supplier)
      Returns a Collector that accumulates the input elements into a new Collection, in encounter order. The Collection is created by the provided supplier.
      Type Parameters:
      T - the type of the input elements
      C - the type of the resulting Collection
      Parameters:
      supplier - a Supplier which returns a new, empty Collection of the appropriate type
      Returns:
      a Collector which collects all the input elements into a Collection, in encounter order

    • toList

      public static <T> RemoteCollector<T,?,List<T>> toList()
      Returns a Collector that accumulates the input elements into a new List. There are no guarantees on the type, mutability, serializability, or thread-safety of the List returned; if more control over the returned List is required, use toCollection(Remote.Supplier).
      Type Parameters:
      T - the type of the input elements
      Returns:
      a Collector which collects all the input elements into a List, in encounter order

    • toUnmodifiableList

      public static <T> RemoteCollector<T,?,List<T>> toUnmodifiableList()
      Returns a Collector that accumulates the input elements into an unmodifiable List in encounter order. The returned Collector disallows null values and will throw NullPointerException if it is presented with a null value.
      Type Parameters:
      T - the type of the input elements
      Returns:
      a Collector that accumulates the input elements into an unmodifiable List in encounter order
      Since:
      10

    • toSortedBag

      public static <T> RemoteCollector<T,?,Collection<T>> toSortedBag()
      Returns a Collector that accumulates the input elements into a new SortedBag.
      Type Parameters:
      T - the type of the input elements
      Returns:
      a Collector which collects all the input elements into a List, in encounter order

    • toSortedBag

      public static <T, E extends Comparable<? super E>> RemoteCollector<T,?,Collection<T>> toSortedBag(ValueExtractor<? super T,? extends E> comparable)
      Returns a Collector that accumulates the input elements into a new SortedBag.
      Type Parameters:
      T - the type of the input elements
      Parameters:
      comparable - a ValueExtractor that returns a Comparable value
      Returns:
      a Collector which collects all the input elements into a List, in encounter order

    • toSortedBag

      public static <T> RemoteCollector<T,?,Collection<T>> toSortedBag(Comparator<? super T> comparator)
      Returns a Collector that accumulates the input elements into a new SortedBag.
      Type Parameters:
      T - the type of the input elements
      Parameters:
      comparator - a comparator for type T
      Returns:
      a Collector which collects all the input elements into a List, in encounter order

    • toSortedBag

      public static <T> RemoteCollector<T,?,Collection<T>> toSortedBag(Remote.Comparator<? super T> comparator)
      Returns a Collector that accumulates the input elements into a new SortedBag.
      Type Parameters:
      T - the type of the input elements
      Parameters:
      comparator - a comparator for type T
      Returns:
      a Collector which collects all the input elements into a List, in encounter order

    • toSet

      public static <T> RemoteCollector<T,?,Set<T>> toSet()
      Returns a Collector that accumulates the input elements into a new Set. There are no guarantees on the type, mutability, serializability, or thread-safety of the Set returned; if more control over the returned Set is required, use toCollection(Remote.Supplier).

      This is an unordered Collector.

      Type Parameters:
      T - the type of the input elements
      Returns:
      a Collector which collects all the input elements into a Set

    • toUnmodifiableSet

      public static <T> RemoteCollector<T,?,Set<T>> toUnmodifiableSet()
      Returns a Collector that accumulates the input elements into an unmodifiable List in encounter order. The returned Collector disallows null values and will throw NullPointerException if it is presented with a null value.
      Type Parameters:
      T - the type of the input elements
      Returns:
      a Collector that accumulates the input elements into an unmodifiable List in encounter order
      Since:
      10

    • toSortedSet

      public static <T> RemoteCollector<T,?,SortedSet<T>> toSortedSet()
      Returns a Collector that accumulates the input elements into a new SortedSet. There are no guarantees on the type, mutability, serializability, or thread-safety of the SortedSet returned; if more control over the returned SortedSet is required, use toCollection(Remote.Supplier).

      This is an unordered Collector.

      Type Parameters:
      T - the type of the input elements
      Returns:
      a Collector which collects all the input elements into a SortedSet

    • toSortedSet

      public static <T, E extends Comparable<? super E>> RemoteCollector<T,?,SortedSet<T>> toSortedSet(ValueExtractor<? super T,? extends E> comparable)
      Returns a Collector that accumulates the input elements into a new SortedSet. There are no guarantees on the type, mutability, serializability, or thread-safety of the SortedSet returned; if more control over the returned SortedSet is required, use toCollection(Remote.Supplier).

      This is an unordered Collector.

      Type Parameters:
      T - the type of the input elements
      Parameters:
      comparable - a ValueExtractor that returns a Comparable value
      Returns:
      a Collector which collects all the input elements into a SortedSet

    • toSortedSet

      public static <T> RemoteCollector<T,?,SortedSet<T>> toSortedSet(Comparator<? super T> comparator)
      Returns a Collector that accumulates the input elements into a new SortedSet. There are no guarantees on the type, mutability, serializability, or thread-safety of the SortedSet returned; if more control over the returned SortedSet is required, use toCollection(Remote.Supplier).

      This is an unordered Collector.

      Type Parameters:
      T - the type of the input elements
      Parameters:
      comparator - a comparator for type T
      Returns:
      a Collector which collects all the input elements into a SortedSet

    • toSortedSet

      public static <T> RemoteCollector<T,?,SortedSet<T>> toSortedSet(Remote.Comparator<? super T> comparator)
      Returns a Collector that accumulates the input elements into a new SortedSet. There are no guarantees on the type, mutability, serializability, or thread-safety of the SortedSet returned; if more control over the returned SortedSet is required, use toCollection(Remote.Supplier).

      This is an unordered Collector.

      Type Parameters:
      T - the type of the input elements
      Parameters:
      comparator - a comparator for type T
      Returns:
      a Collector which collects all the input elements into a SortedSet

    • mapping

      public static <T, U, A, R> RemoteCollector<T,A,R> mapping(Remote.Function<? super T,? extends U> mapper, RemoteCollector<? 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.
      Type Parameters:
      T - the type of the input elements
      U - type of elements accepted by downstream collector
      A - intermediate accumulation type of the downstream collector
      R - result type of collector
      Parameters:
      mapper - a function to be applied to the input elements
      downstream - a collector which will accept mapped values
      Returns:
      a collector which applies the mapping function to the input elements and provides the mapped results to the downstream collector
      API Note:
      The mapping() collectors are most useful when used in a multi-level reduction, such as downstream of a groupingBy or partitioningBy. For example, given a stream of Person, to accumulate the set of last names in each city: 
      
     Map<City, Set<String>> lastNamesByCity
         = people.stream().collect(groupingBy(Person::getCity,
                                              mapping(Person::getLastName,
 toSet())));

    • collectingAndThen

      public static <T, A, R, RR> RemoteCollector<T,A,RR> collectingAndThen(RemoteCollector<T,A,R> downstream, Remote.Function<R,RR> finisher)
      Adapts a Collector to perform an additional finishing transformation. For example, one could adapt the toList() collector to always produce an immutable list with: 
      
     List<String> people
         = people.stream().collect(collectingAndThen(toList(),
 Collections::unmodifiableList));
      Type Parameters:
      T - the type of the input elements
      A - intermediate accumulation type of the downstream collector
      R - result type of the downstream collector
      RR - result type of the resulting collector
      Parameters:
      downstream - a collector
      finisher - a function to be applied to the final result of the downstream collector
      Returns:
      a collector which performs the action of the downstream collector, followed by an additional finishing step

    • counting

      public static <T> RemoteCollector<T,?,Long> counting()
      Returns a Collector accepting elements of type T that counts the number of input elements. If no elements are present, the result is 0.
      Type Parameters:
      T - the type of the input elements
      Returns:
      a Collector that counts the input elements
      Implementation Requirements:
      This produces a result equivalent to: 
      
     reducing(0L, e -> 1L, Long::sum)

    • minBy

      public static <T, E extends Comparable<? super E>> RemoteCollector<T,?,Optional<T>> minBy(ValueExtractor<? super T,? extends E> comparable)
      Returns a Collector that produces the minimal element according to a given Comparable attribute, described as an Optional<T>.
      Type Parameters:
      T - the type of the input elements
      Parameters:
      comparable - a ValueExtractor that returns a Comparable value
      Returns:
      a Collector that produces the minimal value
      Implementation Requirements:
      This produces a result equivalent to: 
      
     reducing(Remote.BinaryOperator.minBy(comparator))

    • minBy

      public static <T> RemoteCollector<T,?,Optional<T>> minBy(Remote.Comparator<? super T> comparator)
      Returns a Collector that produces the minimal element according to a given Comparator, described as an Optional<T>.
      Type Parameters:
      T - the type of the input elements
      Parameters:
      comparator - a Comparator for comparing elements
      Returns:
      a Collector that produces the minimal value
      Implementation Requirements:
      This produces a result equivalent to: 
      
     reducing(Remote.BinaryOperator.minBy(comparator))

    • maxBy

      public static <T, E extends Comparable<? super E>> RemoteCollector<T,?,Optional<T>> maxBy(ValueExtractor<? super T,? extends E> comparable)
      Returns a Collector that produces the maximal element according to a given Comparable attribute, described as an Optional<T>.
      Type Parameters:
      T - the type of the input elements
      Parameters:
      comparable - a ValueExtractor that returns a Comparable value
      Returns:
      a Collector that produces the minimal value
      Implementation Requirements:
      This produces a result equivalent to: 
      
     reducing(Remote.BinaryOperator.minBy(comparator))

    • maxBy

      public static <T> RemoteCollector<T,?,Optional<T>> maxBy(Remote.Comparator<? super T> comparator)
      Returns a Collector that produces the maximal element according to a given Comparator, described as an Optional<T>.
      Type Parameters:
      T - the type of the input elements
      Parameters:
      comparator - a Comparator for comparing elements
      Returns:
      a Collector that produces the maximal value
      Implementation Requirements:
      This produces a result equivalent to: 
      
     reducing(BinaryOperator.maxBy(comparator))

    • summingInt

      public static <T, U> RemoteCollector<T,?,Integer> summingInt(ValueExtractor<? super U,? extends Number> extractor)
      Returns a Collector that produces the sum of a integer-valued function applied to the input elements. If no elements are present, the result is 0.
      Type Parameters:
      T - the type of the stream elements
      U - the type of the objects to extract from, which should be either the same as T, or the key or value type if the T is InvocableMap.Entry
      Parameters:
      extractor - a function extracting the property to be summed
      Returns:
      a Collector that produces the sum of a derived property

    • summingLong

      public static <T, U> RemoteCollector<T,?,Long> summingLong(ValueExtractor<? super U,? extends Number> extractor)
      Returns a Collector that produces the sum of a long-valued function applied to the input elements. If no elements are present, the result is 0.
      Type Parameters:
      T - the type of the stream elements
      U - the type of the objects to extract from, which should be either the same as T, or the key or value type if the T is InvocableMap.Entry
      Parameters:
      extractor - a function extracting the property to be summed
      Returns:
      a Collector that produces the sum of a derived property

    • summingDouble

      public static <T, U> RemoteCollector<T,?,Double> summingDouble(ValueExtractor<? super U,? extends Number> extractor)
      Returns a Collector that produces the sum of a double-valued function applied to the input elements. If no elements are present, the result is 0.

      The sum returned can vary depending upon the order in which values are recorded, due to accumulated rounding error in addition of values of differing magnitudes. Values sorted by increasing absolute magnitude tend to yield more accurate results. If any recorded value is a NaN or the sum is at any point a NaN then the sum will be NaN.

      Type Parameters:
      T - the type of the stream elements
      U - the type of the objects to extract from, which should be either the same as T, or the key or value type if the T is InvocableMap.Entry
      Parameters:
      extractor - a function extracting the property to be summed
      Returns:
      a Collector that produces the sum of a derived property

    • averagingInt

      public static <T, U> RemoteCollector<T,?,Double> averagingInt(ValueExtractor<? super U,? extends Number> extractor)
      Returns a Collector that produces the arithmetic mean of an integer-valued function applied to the input elements. If no elements are present, the result is 0.
      Type Parameters:
      T - the type of the stream elements
      U - the type of the objects to extract from, which should be either the same as T, or the key or value type if the T is InvocableMap.Entry
      Parameters:
      extractor - a function extracting the property to be summed
      Returns:
      a Collector that produces the sum of a derived property

    • averagingLong

      public static <T, U> RemoteCollector<T,?,Double> averagingLong(ValueExtractor<? super U,? extends Number> extractor)
      Returns a Collector that produces the arithmetic mean of a long-valued function applied to the input elements. If no elements are present, the result is 0.
      Type Parameters:
      T - the type of the stream elements
      U - the type of the objects to extract from, which should be either the same as T, or the key or value type if the T is InvocableMap.Entry
      Parameters:
      extractor - a function extracting the property to be averaged
      Returns:
      a Collector that produces the average of a derived property

    • averagingDouble

      public static <T, U> RemoteCollector<T,?,Double> averagingDouble(ValueExtractor<? super U,? extends Number> extractor)
      Returns a Collector that produces the arithmetic mean of a double-valued function applied to the input elements. If no elements are present, the result is 0.

      The average returned can vary depending upon the order in which values are recorded, due to accumulated rounding error in addition of values of differing magnitudes. Values sorted by increasing absolute magnitude tend to yield more accurate results. If any recorded value is a NaN or the sum is at any point a NaN then the average will be NaN.

      Type Parameters:
      T - the type of the stream elements
      U - the type of the objects to extract from, which should be either the same as T, or the key or value type if the T is InvocableMap.Entry
      Parameters:
      extractor - a function extracting the property to be summed
      Returns:
      a Collector that produces the sum of a derived property
      Implementation Note:
      The double format can represent all consecutive integers in the range -253 to 253. If the pipeline has more than 253 values, the divisor in the average computation will saturate at 253, leading to additional numerical errors.

    • reducing

      public static <T> RemoteCollector<T,SimpleHolder<T>,T> reducing(T identity, Remote.BinaryOperator<T> op)
      Returns a Collector which performs a reduction of its input elements under a specified BinaryOperator using the provided identity.
      Type Parameters:
      T - element type for the input and output of the reduction
      Parameters:
      identity - the identity value for the reduction (also, the value that is returned when there are no input elements)
      op - a BinaryOperator<T> used to reduce the input elements
      Returns:
      a Collector which implements the reduction operation
      See Also:
      API Note:
      The reducing() collectors are most useful when used in a multi-level reduction, downstream of groupingBy or partitioningBy. To perform a simple reduction on a stream, use RemoteStream.reduce(Object, BinaryOperator)} instead.

    • reducing

      public static <T> RemoteCollector<T,?,Optional<T>> reducing(Remote.BinaryOperator<T> op)
      Returns a Collector which performs a reduction of its input elements under a specified BinaryOperator. The result is described as an Optional<T>.
      Type Parameters:
      T - element type for the input and output of the reduction
      Parameters:
      op - a BinaryOperator<T> used to reduce the input elements
      Returns:
      a Collector which implements the reduction operation
      See Also:
      API Note:
      The reducing() collectors are most useful when used in a multi-level reduction, downstream of groupingBy or partitioningBy. To perform a simple reduction on a stream, use RemoteStream.reduce(BinaryOperator) instead.

      For example, given a stream of Person, to calculate tallest person in each city: 

      
     Comparator<Person> byHeight = Comparator.comparing(Person::getHeight);
     Map<City, Person> tallestByCity
         = people.stream().collect(groupingBy(Person::getCity,
 reducing(BinaryOperator.maxBy(byHeight))));

    • reducing

      public static <T, U> RemoteCollector<T,?,U> reducing(U identity, Remote.Function<? super T,? extends U> mapper, Remote.BinaryOperator<U> op)
      Returns a Collector which performs a reduction of its input elements under a specified mapping function and BinaryOperator. This is a generalization of reducing(Object, Remote.BinaryOperator) which allows a transformation of the elements before reduction.
      Type Parameters:
      T - the type of the input elements
      U - the type of the mapped values
      Parameters:
      identity - the identity value for the reduction (also, the value that is returned when there are no input elements)
      mapper - a mapping function to apply to each input value
      op - a BinaryOperator<U> used to reduce the mapped values
      Returns:
      a Collector implementing the map-reduce operation
      See Also:
      API Note:
      The reducing() collectors are most useful when used in a multi-level reduction, downstream of groupingBy or partitioningBy. To perform a simple map-reduce on a stream, use RemoteStream.map(Function) and RemoteStream.reduce(Object, BinaryOperator) instead.

      For example, given a stream of Person, to calculate the longest last name of residents in each city: 

      
     Comparator<String> byLength = Comparator.comparing(String::length);
     Map<City, String> longestLastNameByCity
         = people.stream().collect(groupingBy(Person::getCity,
                                              reducing(Person::getLastName,
 BinaryOperator.maxBy(byLength))));

    • reducing

      public static <T, U> RemoteCollector<T,?,U> reducing(U identity, Remote.BiFunction<? super U,? super T,? extends U> mapper, Remote.BinaryOperator<U> op)
      Returns a Collector which performs a reduction of its input elements under a specified mapping function and BinaryOperator. This is a generalization of reducing(Object, Remote.BinaryOperator) which allows a transformation of the elements before reduction.
      Type Parameters:
      T - the type of the input elements
      U - the type of the mapped values
      Parameters:
      identity - the identity value for the reduction (also, the value that is returned when there are no input elements)
      mapper - a mapping function to apply to each input value
      op - a BinaryOperator<U> used to reduce the mapped values
      Returns:
      a Collector implementing the map-reduce operation
      See Also:
      API Note:
      The reducing() collectors are most useful when used in a multi-level reduction, downstream of groupingBy or partitioningBy. To perform a simple map-reduce on a stream, use RemoteStream.map(Function) and RemoteStream.reduce(Object, BinaryOperator) instead.

      For example, given a stream of Person, to calculate the longest last name of residents in each city: 

      
     Comparator<String> byLength = Comparator.comparing(String::length);
     Map<City, String> longestLastNameByCity
         = people.stream().collect(groupingBy(Person::getCity,
                                              reducing(Person::getLastName,
 BinaryOperator.maxBy(byLength))));

    • groupingBy

      public static <T, U, K> RemoteCollector<T,?,Map<K,List<T>>> groupingBy(ValueExtractor<? super U,? 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.

      The classification function maps elements to some key type K. The collector produces a Map<K, List<T>> whose keys are the values resulting from applying the classification function to the input elements, and whose corresponding values are Lists containing the input elements which map to the associated key under the classification function.

      There are no guarantees on the type, mutability, serializability, or thread-safety of the Map or List objects returned.

      Type Parameters:
      T - the type of the stream elements
      U - the type of the objects to extract from, which should be either the same as T, or the key or value type if the T is InvocableMap.Entry
      K - the type of the keys
      Parameters:
      classifier - the classifier function mapping input elements to keys
      Returns:
      a Collector implementing the group-by operation
      See Also:
      Implementation Requirements:
      This produces a result similar to: 
      
     groupingBy(classifier, toList());

    • groupingBy

      public static <T, U, K, A, D> RemoteCollector<T,?,Map<K,D>> groupingBy(ValueExtractor<? super U,? extends K> classifier, RemoteCollector<? 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.

      The classification function maps elements to some key type K. The downstream collector operates on elements of type T and produces a result of type D. The resulting collector produces a Map<K, D>.

      There are no guarantees on the type, mutability, serializability, or thread-safety of the Map returned.

      For example, to compute the set of last names of people in each city: 

      
     Map<City, Set<String>> namesByCity
         = people.stream().collect(groupingBy(Person::getCity,
                                              mapping(Person::getLastName,
 toSet())));
      Type Parameters:
      T - the type of the stream elements
      U - the type of the objects to extract from, which should be either the same as T, or the key or value type if the T is InvocableMap.Entry
      K - the type of the keys
      A - the intermediate accumulation type of the downstream collector
      D - the result type of the downstream reduction
      Parameters:
      classifier - a classifier function mapping input elements to keys
      downstream - a Collector implementing the downstream reduction
      Returns:
      a Collector implementing the cascaded group-by operation
      See Also:

    • groupingBy

      public static <T, U, K, D, A, M extends Map<K, D>> RemoteCollector<T,?,M> groupingBy(ValueExtractor<? super U,? extends K> extractor, Remote.Supplier<M> mapFactory, RemoteCollector<? 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. The Map produced by the Collector is created with the supplied factory function.

      The classification function maps elements to some key type K. The downstream collector operates on elements of type T and produces a result of type D. The resulting collector produces a Map<K, D>.

      For example, to compute the set of last names of people in each city, where the city names are sorted: 

      
     Map<City, Set<String>> namesByCity
         = people.stream().collect(groupingBy(Person::getCity,
 TreeMap::new,
                                              mapping(Person::getLastName,
 toSet())));
      Type Parameters:
      T - the type of the stream elements
      U - the type of the objects to extract from, which should be either the same as T, or the key or value type if the T is InvocableMap.Entry
      K - the type of the keys
      D - the result type of the downstream reduction
      A - the intermediate accumulation type of the downstream collector
      M - the type of the resulting Map
      Parameters:
      extractor - an extractor function mapping input elements to keys
      mapFactory - a function which, when called, produces a new empty Map of the desired type
      downstream - a Collector implementing the downstream reduction
      Returns:
      a Collector implementing the cascaded group-by operation
      See Also:

    • toMap

      public static <T, U1, U2, K, V> RemoteCollector<T,?,Map<K,V>> toMap(ValueExtractor<? super U1,? extends K> keyMapper, ValueExtractor<? super U2,? extends V> 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.

      If the mapped keys contains duplicates (according to Object.equals(Object)), an IllegalStateException is thrown when the collection operation is performed. If the mapped keys may have duplicates, use toMap(ValueExtractor, ValueExtractor, Remote.BinaryOperator) instead.

      Type Parameters:
      T - the type of the stream elements
      U1 - the type of the objects to extract keys from, which should be either the same as T, or the key or value type if the T is InvocableMap.Entry
      U2 - the type of the objects to extract values from, which should be either the same as T, or the key or value type if the T is InvocableMap.Entry
      K - the output type of the key mapping function
      V - the output type of the value mapping function
      Parameters:
      keyMapper - a mapping function to produce keys
      valueMapper - a mapping function to produce values
      Returns:
      a Collector which collects elements into a Map whose keys and values are the result of applying mapping functions to the input elements
      See Also:

    • toUnmodifiableMap

      public static <T, U1, U2, K, V> RemoteCollector<T,?,Map<K,V>> toUnmodifiableMap(ValueExtractor<? super U1,? extends K> keyMapper, ValueExtractor<? super U2,? extends V> valueMapper)
      Returns a Collector that accumulates elements into an unmodifiable Map whose keys and values are the result of applying the provided mapping functions to the input elements.

      If the mapped keys contains duplicates (according to Object.equals(Object)), an IllegalStateException is thrown when the collection operation is performed. If the mapped keys may have duplicates, use toMap(ValueExtractor, ValueExtractor, Remote.BinaryOperator) instead.

      Type Parameters:
      T - the type of the stream elements
      U1 - the type of the objects to extract keys from, which should be either the same as T, or the key or value type if the T is InvocableMap.Entry
      U2 - the type of the objects to extract values from, which should be either the same as T, or the key or value type if the T is InvocableMap.Entry
      K - the output type of the key mapping function
      V - the output type of the value mapping function
      Parameters:
      keyMapper - a mapping function to produce keys
      valueMapper - a mapping function to produce values
      Returns:
      a Collector which collects elements into an unmodifiable Map whose keys and values are the result of applying mapping functions to the input elements
      Since:
      22.09
      See Also:

    • toMap

      public static <T, U1, U2, K, V> RemoteCollector<T,?,Map<K,V>> toMap(ValueExtractor<? super U1,? extends K> keyMapper, ValueExtractor<? super U2,? extends V> valueMapper, Remote.BinaryOperator<V> 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.

      If the mapped keys contains duplicates (according to Object.equals(Object)), the value mapping function is applied to each equal element, and the results are merged using the provided merging function.

      Type Parameters:
      T - the type of the stream elements
      U1 - the type of the objects to extract keys from, which should be either the same as T, or the key or value type if the T is InvocableMap.Entry
      U2 - the type of the objects to extract values from, which should be either the same as T, or the key or value type if the T is InvocableMap.Entry
      K - the output type of the key mapping function
      V - the output type of the value mapping function
      Parameters:
      keyMapper - a mapping function to produce keys
      valueMapper - a mapping function to produce values
      mergeFunction - a merge function, used to resolve collisions between values associated with the same key, as supplied to Map.merge(Object, Object, BiFunction)
      Returns:
      a Collector which collects elements into a Map whose keys are the result of applying a key mapping function to the input elements, and whose values are the result of applying a value mapping function to all input elements equal to the key and combining them using the merge function
      See Also:

    • toUnmodifiableMap

      public static <T, U1, U2, K, V> RemoteCollector<T,?,Map<K,V>> toUnmodifiableMap(ValueExtractor<? super U1,? extends K> keyMapper, ValueExtractor<? super U2,? extends V> valueMapper, Remote.BinaryOperator<V> mergeFunction)
      Returns a Collector that accumulates elements into an unmodifiable Map whose keys and values are the result of applying the provided mapping functions to the input elements.

      If the mapped keys contains duplicates (according to Object.equals(Object)), the value mapping function is applied to each equal element, and the results are merged using the provided merging function.

      Type Parameters:
      T - the type of the stream elements
      U1 - the type of the objects to extract keys from, which should be either the same as T, or the key or value type if the T is InvocableMap.Entry
      U2 - the type of the objects to extract values from, which should be either the same as T, or the key or value type if the T is InvocableMap.Entry
      K - the output type of the key mapping function
      V - the output type of the value mapping function
      Parameters:
      keyMapper - a mapping function to produce keys
      valueMapper - a mapping function to produce values
      mergeFunction - a merge function, used to resolve collisions between values associated with the same key, as supplied to Map.merge(Object, Object, BiFunction)
      Returns:
      a Collector which collects elements into an unmodifiable Map whose keys and values are the result of applying mapping functions to the input elements, and whose values are the result of applying a value mapping function to all input elements equal to the key and combining them using the merge function
      Since:
      22.09
      See Also:

    • toMap

      public static <T, U1, U2, K, V, M extends Map<K, V>> RemoteCollector<T,?,M> toMap(ValueExtractor<? super U1,? extends K> keyExtractor, ValueExtractor<? super U2,? extends V> valueExtractor, Remote.BinaryOperator<V> mergeFunction, Remote.Supplier<M> mapSupplier)
      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.

      If the mapped keys contains duplicates (according to Object.equals(Object)), the value mapping function is applied to each equal element, and the results are merged using the provided merging function. The Map is created by a provided supplier function.

      Type Parameters:
      T - the type of the stream elements
      U1 - the type of the objects to extract keys from, which should be either the same as T, or the key or value type if the T is InvocableMap.Entry
      U2 - the type of the objects to extract values from, which should be either the same as T, or the key or value type if the T is InvocableMap.Entry
      K - the output type of the key mapping function
      V - the output type of the value mapping function
      M - the type of the resulting Map
      Parameters:
      keyExtractor - a mapping function to produce keys
      valueExtractor - a mapping function to produce values
      mergeFunction - a merge function, used to resolve collisions between values associated with the same key, as supplied to Map.merge(Object, Object, BiFunction)
      mapSupplier - a function which returns a new, empty Map into which the results will be inserted
      Returns:
      a Collector which collects elements into a Map whose keys are the result of applying a key mapping function to the input elements, and whose values are the result of applying a value mapping function to all input elements equal to the key and combining them using the merge function
      See Also:

    • toConcurrentMap

      public static <T, U1, U2, K, V> RemoteCollector<T,?,ConcurrentMap<K,V>> toConcurrentMap(ValueExtractor<? super U1,? extends K> keyMapper, ValueExtractor<? super U2,? extends V> 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.

      If the mapped keys contain duplicates (according to Object.equals(Object)), an IllegalStateException is thrown when the collection operation is performed. If the mapped keys may have duplicates, use toConcurrentMap(ValueExtractor, ValueExtractor, Remote.BinaryOperator) instead.

      There are no guarantees on the type or mutability of the ConcurrentMap returned.

      Type Parameters:
      T - the type of the input elements
      K - the output type of the key mapping function
      V - the output type of the value mapping function
      Parameters:
      keyMapper - the mapping function to produce keys
      valueMapper - the mapping function to produce values
      Returns:
      a concurrent, unordered Collector which collects elements into a ConcurrentMap whose keys are the result of applying a key mapping function to the input elements, and whose values are the result of applying a value mapping function to the input elements
      See Also:

    • toConcurrentMap

      public static <T, U1, U2, K, V> RemoteCollector<T,?,ConcurrentMap<K,V>> toConcurrentMap(ValueExtractor<? super U1,? extends K> keyMapper, ValueExtractor<? super U2,? extends V> valueMapper, Remote.BinaryOperator<V> 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.

      If the mapped keys contain duplicates (according to Object.equals(Object)), the value mapping function is applied to each equal element, and the results are merged using the provided merging function.

      There are no guarantees on the type, mutability, or serializability of the ConcurrentMap returned.

      Type Parameters:
      T - the type of the input elements
      K - the output type of the key mapping function
      V - the output type of the value mapping function
      Parameters:
      keyMapper - a mapping function to produce keys
      valueMapper - a mapping function to produce values
      mergeFunction - a merge function, used to resolve collisions between values associated with the same key, as supplied to Map.merge(Object, Object, BiFunction)
      Returns:
      a concurrent, unordered Collector which collects elements into a ConcurrentMap whose keys are the result of applying a key mapping function to the input elements, and whose values are the result of applying a value mapping function to all input elements equal to the key and combining them using the merge function
      See Also:
      API Note:
      There are multiple ways to deal with collisions between multiple elements mapping to the same key. The other forms of toConcurrentMap simply use a merge function that throws unconditionally, but you can easily write more flexible merge policies. For example, if you have a stream of Person, and you want to produce a "phone book" mapping name to address, but it is possible that two persons have the same name, you can do as follows to gracefully deal with these collisions, and produce a ConcurrentMap mapping names to a concatenated list of addresses: 
      
 ConcurrentMap<String, String> phoneBook
   = people.stream().collect(
     toConcurrentMap(Person::getName,
                     Person::getAddress,
                     (s, a) -> s + ", " + a));

      This is a concurrent and unordered Collector.

    • summarizingInt

      public static <T, U> RemoteCollector<T,?,com.tangosol.internal.util.IntSummaryStatistics> summarizingInt(ValueExtractor<? super U,? extends Number> extractor)
      Returns a Collector which applies an int-producing mapping function to each input element, and returns summary statistics for the resulting values.
      Type Parameters:
      T - the type of the stream elements
      U - the type of the objects to extract from, which should be either the same as T, or the key or value type if the T is InvocableMap.Entry
      Parameters:
      extractor - a mapping function to apply to each element
      Returns:
      a Collector implementing the summary-statistics reduction
      See Also:

    • summarizingLong

      public static <T, U> RemoteCollector<T,?,com.tangosol.internal.util.LongSummaryStatistics> summarizingLong(ValueExtractor<? super U,? extends Number> extractor)
      Returns a Collector which applies an long-producing mapping function to each input element, and returns summary statistics for the resulting values.
      Type Parameters:
      T - the type of the stream elements
      U - the type of the objects to extract from, which should be either the same as T, or the key or value type if the T is InvocableMap.Entry
      Parameters:
      extractor - a mapping function to apply to each element
      Returns:
      a Collector implementing the summary-statistics reduction
      See Also:

    • summarizingDouble

      public static <T, U> RemoteCollector<T,?,com.tangosol.internal.util.DoubleSummaryStatistics> summarizingDouble(ValueExtractor<? super U,? extends Number> extractor)
      Returns a Collector which applies an double-producing mapping function to each input element, and returns summary statistics for the resulting values.
      Type Parameters:
      T - the type of the stream elements
      U - the type of the objects to extract from, which should be either the same as T, or the key or value type if the T is InvocableMap.Entry
      Parameters:
      extractor - a mapping function to apply to each element
      Returns:
      a Collector implementing the summary-statistics reduction
      See Also: