org.perro.functions.predicate

Class FilterUtils

java.lang.Object

org.perro.functions.predicate.FilterUtils

public final class FilterUtils
extends java.lang.Object

Convenience methods for filtering collections of objects, without having to spell out the entire stream->filter->collect process.

Method Summary

Modifier and Type	Method and Description
static <T,C extends java.util.Collection<T>> C	filter(java.util.Collection<T> objects, org.perro.functions.predicate.FilterCollector<T,C> filterCollector) Filters a collection of objects, based a predicate, into a Collection.
static <T> java.util.List<T>	filter(java.util.Collection<T> objects, java.util.function.Predicate<T> predicate) Filters a Collection of objects, based a predicate, into a list.
static <T,C extends java.util.Collection<T>> org.perro.functions.predicate.FilterCollector<T,C>	filterAndThen(java.util.function.Predicate<T> filter, java.util.stream.Collector<T,?,C> collector) Builds an object combining a Predicate and a Collector for use in the filter(Collection, FilterCollector) method.
static <T> java.util.List<T>	filterDistinct(java.util.Collection<T> objects, java.util.function.Predicate<T> predicate) Filters a Collection of objects, based a predicate, into a list of distinct instances (according to Object.equals(Object)).
static <T> java.util.Set<T>	filterToSet(java.util.Collection<T> objects, java.util.function.Predicate<T> predicate) Filters a Collection of objects, based a predicate, into a set.

Methods inherited from class java.lang.Object

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

Method Detail

filter

public static <T> java.util.List<T> filter(java.util.Collection<T> objects,
                                           java.util.function.Predicate<T> predicate)

Filters a Collection of objects, based a predicate, into a list.

Type Parameters:

T - The target element type for the objects Collection.

Parameters:

objects - A collection of objects of type <T> to be filtered.

predicate - A predicate with which to filter the objects collection. The provided predicate will be made null-safe, and if the target is null, then the predicate will return false.

Returns:

A List of objects filtered from the objects Collection.

filterToSet

public static <T> java.util.Set<T> filterToSet(java.util.Collection<T> objects,
                                               java.util.function.Predicate<T> predicate)

Filters a Collection of objects, based a predicate, into a set.

Type Parameters:

T - The target element type for the objects Collection.

Parameters:

objects - A collection of objects of type <T> to be filtered.

predicate - A predicate with which to filter the objects collection. The provided predicate will be made null-safe, and if the target is null, then the predicate will return false.

Returns:

A Set of objects filtered from the objects Collection.

filterDistinct

public static <T> java.util.List<T> filterDistinct(java.util.Collection<T> objects,
                                                   java.util.function.Predicate<T> predicate)

Filters a Collection of objects, based a predicate, into a list of distinct instances (according to Object.equals(Object)).

Type Parameters:

T - The target element type for the objects Collection.

Parameters:

objects - A Collection of objects of type <T> to be filtered.

predicate - A predicate with which to filter the objects collection. The provided predicate will be made null-safe, and if the target is null, then the predicate will return false.

Returns:

A List of objects filtered from the objects Collection.

filter

public static <T,C extends java.util.Collection<T>> C filter(java.util.Collection<T> objects,
                                                             org.perro.functions.predicate.FilterCollector<T,C> filterCollector)

Filters a collection of objects, based a predicate, into a Collection. This overload takes an object that is built using the filterAndThen(Predicate, Collector) method, which allows you to specify both a predicate and a Collector to build any type of Collection as a result. For example:

     Collection<Widget> widgets = ...
     List<Widget> = FilterUtils.filter(widgets, FilterUtils.filterAndThen(Widget::isConsumerProduct, Collectors.toCollection(LinkedList::new)));
 

Or, with static imports:

     filter(widgets, filterAndThen(Widget::isConsumerProduct, toCollection(LinkedList::new)));
 

Type Parameters:

T - The target element type for the objects Collection.

C - The type of the resulting Collection.

Parameters:

objects - A Collection of objects of type <T> to be filtered.

filterCollector - An object containing a predicate with which to filter the objects Collection, and a Collector to accumulate results into a Collection.

Returns:

A Collection of objects filtered from the objects Collection.

filterAndThen

public static <T,C extends java.util.Collection<T>> org.perro.functions.predicate.FilterCollector<T,C> filterAndThen(java.util.function.Predicate<T> filter,
                                                                                                                     java.util.stream.Collector<T,?,C> collector)

Builds an object combining a Predicate and a Collector for use in the filter(Collection, FilterCollector) method.

Type Parameters:

T - The target element type for a collection to be filtered.

C - The type of the resulting Collection.

Parameters:

filter - A Predicate for filtering elements from a Collection of objects. The provided predicate will be made null-safe, and if the target is null, then the predicate will return false.

collector - A Collector to accumulating elements into a Collection of any type.

Returns:

A Collection of any type containing objects filtered from an input Collection.