org.perro.functions.mapper

Class TransformUtils

java.lang.Object

org.perro.functions.mapper.TransformUtils

public final class TransformUtils
extends java.lang.Object

Methods to transform a collection of elements of a given type, to those of another type, in some cases to another type of collection as well.

Method Summary

Modifier and Type	Method and Description
static <T,U,C extends java.util.Collection<U>> C	flatMap(java.util.Collection<T> objects, org.perro.functions.mapper.FlatMapCollector<T,U,C> flatMapCollector) Given a collection of elements of type <T>, and an object that represents a transformer Function<T, Collection<U>> along with a Collector<U, ?, C>, this method collects all of those individual collections into one resulting Collection of type <C>, consisting of all of the elements.
static <T,U> java.util.List<U>	flatMap(java.util.Collection<T> objects, java.util.function.Function<T,java.util.Collection<U>> function) Given a collection of elements of type <T>, and a Function that transforms each of those elements into collections of type <U>, this method collects all of those individual collections into one resulting List consisting of all of the elements.
static <T,U,C extends java.util.Collection<U>> org.perro.functions.mapper.FlatMapCollector<T,U,C>	flatMapAndThen(java.util.function.Function<T,java.util.Collection<U>> flatMapper, java.util.stream.Collector<U,?,C> collector) Given a Function<T, Collection<U>>, and a Collector<U, ?, C>, this method builds an object consisting of both of those parameters.
static <T,U> java.util.List<U>	flatMapDistinct(java.util.Collection<T> objects, java.util.function.Function<T,java.util.Collection<U>> function) Given a collection of elements of type <T>, and a Function that transforms each of those elements into collections of type <U>, this method collects all of those individual collections into one resulting List consisting of all of the distinct elements of type <U> (according to Object.equals(Object)).
static <T,R> java.util.Set<R>	flatMapToSet(java.util.Collection<T> objects, java.util.function.Function<T,java.util.Collection<R>> function) Given a collection of elements of type <T>, and a Function that transforms each of those elements into collections of type <R>, this method collects all of those individual collections into one resulting Set consisting of all of the elements.
static <T,R> java.util.List<R>	transform(java.util.Collection<T> objects, java.util.function.Function<T,R> transformer) Given a collection of elements of type <T>, and a transformer function that converts those elements to objects of type <R>, this method transforms the given collection to a List<R>.
static <T,U,C extends java.util.Collection<U>> C	transform(java.util.Collection<T> objects, org.perro.functions.mapper.TransformerCollector<T,U,C> transformerCollector) Given a collection of elements of type <T>, and an object that represents a transformer Function<T, U> along with a Collector<U, ?, C>, this method transforms the given collection to one of type <C>, with elements of type <U>.
static <T,U,C extends java.util.Collection<U>> org.perro.functions.mapper.TransformerCollector<T,U,C>	transformAndThen(java.util.function.Function<T,U> transformer, java.util.stream.Collector<U,?,C> collector) Given a Function<T, U>, and a Collector<U, ?, C>, this method builds an object consisting of both of those parameters.
static <T,R> java.util.List<R>	transformDistinct(java.util.Collection<T> objects, java.util.function.Function<T,R> transformer) Given a collection of elements of type <T>, and a transformer function that converts those elements to objects of type <R>, this method transforms the given collection to a List<R> of distinct elements (according to Object.equals(Object)).
static <T,K,V> java.util.Map<K,V>	transformToMap(java.util.Collection<T> objects, org.perro.functions.mapper.KeyValueMapper<T,K,V> keyValueMapper) Given a collection of elements of type <T>, and an object that represents a transformer of those elements into Map keys and values, of type <K> and <V> respectively, this method transforms that collection into a Map<K, V>.
static <T,R> java.util.Set<R>	transformToSet(java.util.Collection<T> objects, java.util.function.Function<T,R> transformer) Given a collection of elements of type <T>, and a transformer function that converts those elements to objects of type <R>, this method transforms the given collection to a Set<R>.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

transform

public static <T,R> java.util.List<R> transform(java.util.Collection<T> objects,
                                                java.util.function.Function<T,R> transformer)

Given a collection of elements of type <T>, and a transformer function that converts those elements to objects of type <R>, this method transforms the given collection to a List<R>.

Type Parameters:

T - The type of the elements of the passed objects Collection.

R - The type of the elements in the resulting List.

Parameters:

objects - A collection of elements of type <T>.

transformer - A transformer Function from objects of type <T>, to objects of type <R>.

Returns:

A List<R> consisting of the elements of the passed objects Collection, transformed into objects of type <R>.

transformToSet

public static <T,R> java.util.Set<R> transformToSet(java.util.Collection<T> objects,
                                                    java.util.function.Function<T,R> transformer)

Given a collection of elements of type <T>, and a transformer function that converts those elements to objects of type <R>, this method transforms the given collection to a Set<R>.

Type Parameters:

T - The type of the elements of the passed objects Collection.

R - The type of the elements in the resulting Set.

Parameters:

objects - A collection of elements of type <T>.

transformer - A transformer Function from objects of type <T>, to objects of type <R>.

Returns:

A Set<R> consisting of the elements of the passed objects Collection, transformed into objects of type <R>.

transformDistinct

public static <T,R> java.util.List<R> transformDistinct(java.util.Collection<T> objects,
                                                        java.util.function.Function<T,R> transformer)

Given a collection of elements of type <T>, and a transformer function that converts those elements to objects of type <R>, this method transforms the given collection to a List<R> of distinct elements (according to Object.equals(Object)).

Type Parameters:

T - The type of the elements of the passed objects Collection.

R - The type of the elements in the resulting List.

Parameters:

objects - A collection of elements of type <T>.

transformer - A transformer Function from objects of type <T>, to objects of type <R>.

Returns:

A List<R> consisting of the elements of the passed objects Collection, transformed into objects of type <R>. The resulting List will contain only distinct elements of type <R>.

transform

public static <T,U,C extends java.util.Collection<U>> C transform(java.util.Collection<T> objects,
                                                                  org.perro.functions.mapper.TransformerCollector<T,U,C> transformerCollector)

Given a collection of elements of type <T>, and an object that represents a transformer Function<T, U> along with a Collector<U, ?, C>, this method transforms the given collection to one of type <C>, with elements of type <U>.

Type Parameters:

T - The type of the elements in the passed objects Collection.

U - The type of the elements in the resulting collection.

C - The type of the resulting Collection.

Parameters:

objects - A collection of elements of type <T>.

transformerCollector - An object that represents a transformer Function<T, U> along with a Collector<U, ?, C>.

Returns:

A Collection of type <C>, containing elements of type <U>, transformed from the elements of the passed objects Collection.

transformToMap

public static <T,K,V> java.util.Map<K,V> transformToMap(java.util.Collection<T> objects,
                                                        org.perro.functions.mapper.KeyValueMapper<T,K,V> keyValueMapper)

Given a collection of elements of type <T>, and an object that represents a transformer of those elements into Map keys and values, of type <K> and <V> respectively, this method transforms that collection into a Map<K, V>.

Type Parameters:

T - The type of the elements in the passed objects Collection.

K - The type of the keys in the resulting Map.

V - The type of the values in the resulting Map.

Parameters:

objects - A collection of elements of type <T>.

keyValueMapper - An object consisting of a pair of functions, one transforming an element of type <T> into a key value of type <K>, and the other transforming <T> into a value of <V>.

Returns:

A Map<K, V> with the keys and values both transformed from elements of type <T>.

flatMap

public static <T,U> java.util.List<U> flatMap(java.util.Collection<T> objects,
                                              java.util.function.Function<T,java.util.Collection<U>> function)

Given a collection of elements of type <T>, and a Function that transforms each of those elements into collections of type <U>, this method collects all of those individual collections into one resulting List consisting of all of the elements.

Type Parameters:

T - The type of the elements in the passed objects Collection.

U - The type of the elements in the resulting collection.

Parameters:

objects - A collection of elements of type <T>.

function - A transformer Function from objects of type <T>, to a Collection of elements of type <U>.

Returns:

A List consisting of all of the elements, of all the collections transformed from individual elements of the passed objects collection.

flatMapToSet

public static <T,R> java.util.Set<R> flatMapToSet(java.util.Collection<T> objects,
                                                  java.util.function.Function<T,java.util.Collection<R>> function)

Given a collection of elements of type <T>, and a Function that transforms each of those elements into collections of type <R>, this method collects all of those individual collections into one resulting Set consisting of all of the elements.

Type Parameters:

T - The type of the elements in the passed objects Collection.

R - The type of the elements in the resulting collection.

Parameters:

objects - A collection of elements of type <T>.

function - A transformer Function from objects of type <T>, to objects of type <R>.

Returns:

A Set consisting of all of the elements, of all the collections transformed from individual elements of the passed objects collection.

flatMapDistinct

public static <T,U> java.util.List<U> flatMapDistinct(java.util.Collection<T> objects,
                                                      java.util.function.Function<T,java.util.Collection<U>> function)

Given a collection of elements of type <T>, and a Function that transforms each of those elements into collections of type <U>, this method collects all of those individual collections into one resulting List consisting of all of the distinct elements of type <U> (according to Object.equals(Object)).

Type Parameters:

T - The type of the elements in the passed objects Collection.

U - The type of the elements in the resulting collection.

Parameters:

objects - A collection of elements of type <T>.

function - A transformer Function from objects of type <T>, to objects of type <U>.

Returns:

A List consisting of all of the distinct elements, of all the collections transformed from individual elements of the passed objects collection.

flatMap

public static <T,U,C extends java.util.Collection<U>> C flatMap(java.util.Collection<T> objects,
                                                                org.perro.functions.mapper.FlatMapCollector<T,U,C> flatMapCollector)

Given a collection of elements of type <T>, and an object that represents a transformer Function<T, Collection<U>> along with a Collector<U, ?, C>, this method collects all of those individual collections into one resulting Collection of type <C>, consisting of all of the elements.

Type Parameters:

T - The type of the elements in the passed objects Collection.

U - The type of the elements in the resulting collection.

C - The type of the resulting Collection.

Parameters:

objects - A collection of elements of type <T>.

flatMapCollector - An object that represents a transformer Function<T, Collection<U>> along with a Collector<U, ?, C>.

Returns:

A Collection of type <C>, containing elements of type <U>, transformed from the elements of the passed objects Collection.

transformAndThen

public static <T,U,C extends java.util.Collection<U>> org.perro.functions.mapper.TransformerCollector<T,U,C> transformAndThen(java.util.function.Function<T,U> transformer,
                                                                                                                              java.util.stream.Collector<U,?,C> collector)

Given a Function<T, U>, and a Collector<U, ?, C>, this method builds an object consisting of both of those parameters. This method is meant to build the second parameter of the transform(Collection, TransformerCollector) method. For example, suppose you want to retrieve an EnumSet consisting of all the unique ProductLine enumerated values in the line items of an order:

     private Set<ProductLine> getUniqueProductLines(Order order) {
         return TransformUtils.transform(order.getLineItems(),
             TransformUtils.transformAndThen(LineItem::getProductLine, CollectorUtils.toEnumSet(ProductLine.class)));
     }
 

Or, using static imports:

     private Set<ProductLine> getUniqueProductLines(Order order) {
         return transform(order.getLineItems(), transformAndThen(LineItem::getProductLine, toEnumSet(ProductLine.class)));
     }
 

Type Parameters:

T - The type of the target element to be passed into the transformer function.

U - The type of the return value of the transformer function.

C - The type of the resulting collection of the passed Collector.

Parameters:

transformer - A transformer Function from objects of type <T>, to objects of type <U>.

collector - A Collector<U, ?, C> to return a Collection of elements of type <C>.

Returns:

Builds an object consisting of a transformer Function, along with a Collector.

flatMapAndThen

public static <T,U,C extends java.util.Collection<U>> org.perro.functions.mapper.FlatMapCollector<T,U,C> flatMapAndThen(java.util.function.Function<T,java.util.Collection<U>> flatMapper,
                                                                                                                        java.util.stream.Collector<U,?,C> collector)

Given a Function<T, Collection<U>>, and a Collector<U, ?, C>, this method builds an object consisting of both of those parameters. This method is meant to build the second parameter of the flatMap(Collection, FlatMapCollector) method. For example, suppose you want to retrieve an EnumSet consisting of all the unique ProductLine enumerated values for a Collection of customer orders:

     private Set<ProductLine> getUniqueProductLines(Collection<Order> customerOrders) {
         return TransformUtils.flatMap(order.getLineItems(),
             TransformUtils.flatMapAndThen(Order::getProductLines, CollectorUtils.toEnumSet(ProductLine.class)));
     }
 

Or, using static imports:

     private Set<ProductLine> getUniqueProductLines(Collection<Order> customerOrders) {
         return flatMap(order.getLineItems(), flatMapAndThen(Order::getProductLines, toEnumSet(ProductLine.class)));
     }
 

Type Parameters:

T - The type of the target element to be passed into the transformer function.

U - The type of the elements in the Collection to be returned from the transformer function.

C - The type of the resulting collection of the passed Collector.

Parameters:

flatMapper - A transformer Function from objects of type <T>, to a Collection of elements of type <U>.

collector - A Collector<U, ?, C> to return a Collection of elements of type <C>.

Returns:

Builds an object consisting of a transformer Function, along with a Collector.