Package com.commercetools.sync.commons.utils

Class CollectionUtils

java.lang.Object

com.commercetools.sync.commons.utils.CollectionUtils

public final class CollectionUtils
extends java.lang.Object

Method Summary

Modifier and Type	Method	Description
static <T,K> java.util.Map<K,T>	collectionToMap(java.util.Collection<T> collection, java.util.function.Function<? super T,? extends K> keyMapper)	Same as collectionToMap(Collection, Function, Function), but uses entries themselves as map values.
static <T,K,V> java.util.Map<K,V>	collectionToMap(java.util.Collection<T> collection, java.util.function.Function<? super T,? extends K> keyMapper, java.util.function.Function<? super T,? extends V> valueMapper)	Convert a collection to a map using keyMapper and valueMapper mappers.
static <T,K> java.util.Set<K>	collectionToSet(java.util.Collection<T> collection, java.util.function.Function<? super T,? extends K> keyMapper)	Convert a collection to a set of values using keyMapper mapping.
static <T> java.util.Collection<T>	emptyIfNull(java.util.Collection<T> collection)	Safe wrapper around nullable collection instances: returns collection argument itself, if the collection is non-null, otherwise returns (immutable) empty collection.
static <T> java.util.List<T>	emptyIfNull(java.util.List<T> list)	Safe wrapper around nullable list instances: returns list argument itself, if the list is non-null, otherwise returns (immutable) empty list.
static <K,V> java.util.Map<K,V>	emptyIfNull(java.util.Map<K,V> map)	Safe wrapper around nullable map instances: returns map argument itself, if the map is non-null, otherwise returns (immutable) empty map.
static <T> java.util.Set<T>	emptyIfNull(java.util.Set<T> set)	Safe wrapper around nullable set instances: returns set argument itself, if the set is non-null, otherwise returns (immutable) empty set.
static <T> java.util.stream.Stream<T>	filterCollection(java.util.Collection<T> collection, java.util.function.Predicate<T> includeCondition)	Create a new collection which contains only elements which satisfy includeCondition predicate.

Methods inherited from class java.lang.Object

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

Method Detail

filterCollection

@Nonnull
public static <T> java.util.stream.Stream<T> filterCollection(@Nullable
                                                              java.util.Collection<T> collection,
                                                              @Nonnull
                                                              java.util.function.Predicate<T> includeCondition)

Create a new collection which contains only elements which satisfy includeCondition predicate.

Type Parameters:

T - type of the collection items.

Parameters:

collection - Collection to be filtered

includeCondition - condition which verifies whether the value should be included to the final result.

Returns:

new filtered stream with items which satisfy includeCondition predicate. If collection is null or empty - empty stream is returned.

collectionToSet

@Nonnull
public static <T,K> java.util.Set<K> collectionToSet(@Nullable
                                                           java.util.Collection<T> collection,
                                                           @Nonnull
                                                           java.util.function.Function<? super T,? extends K> keyMapper)

Convert a collection to a set of values using keyMapper mapping.

If the collection has duplicate keys - only one will be stored, which one is not defined though.

Type Parameters:

T - type of collection entries

K - type of Set key

Parameters:

collection - Collection to convert

keyMapper - function which converts the collection entry to a key.

Returns:

new Set which consists of items, converted from <T> entries to keys using entryToKey function.

collectionToMap

@Nonnull
public static <T,K,V> java.util.Map<K,V> collectionToMap(@Nullable
                                                                           java.util.Collection<T> collection,
                                                                           @Nonnull
                                                                           java.util.function.Function<? super T,? extends K> keyMapper,
                                                                           @Nonnull
                                                                           java.util.function.Function<? super T,? extends V> valueMapper)

Convert a collection to a map using keyMapper and valueMapper mappers. If keys are duplicated - only one value is stored, which one - undefined.

Type Parameters:

T - type of collection entries

K - type of Map key

V - type of Map value

Parameters:

collection - Collection to convert

keyMapper - function which converts the collection entry to a key

valueMapper - function which converts the collection entry to a value

Returns:

new Map which consists of key-value pairs, converted from <T> entries

See Also:

collectionToMap(Collection, Function)

collectionToMap

@Nonnull
public static <T,K> java.util.Map<K,T> collectionToMap(@Nullable
                                                                   java.util.Collection<T> collection,
                                                                   @Nonnull
                                                                   java.util.function.Function<? super T,? extends K> keyMapper)

Same as collectionToMap(Collection, Function, Function), but uses entries themselves as map values.

Type Parameters:

T - type of collection entries

K - type of Map key

Parameters:

collection - Collection to convert

keyMapper - function which converts the collection entry to a key

Returns:

new Map which consists of key-value pairs, converted from <T> entries

See Also:

collectionToMap(Collection, Function, Function)

emptyIfNull

@Nonnull
public static <T> java.util.Collection<T> emptyIfNull(@Nullable
                                                      java.util.Collection<T> collection)

Safe wrapper around nullable collection instances: returns collection argument itself, if the collection is non-null, otherwise returns (immutable) empty collection.

Type Parameters:

T - collection entities type

Parameters:

collection - Collection instance to process

Returns:

original collection instance, if non-null; otherwise immutable empty collection instance.

See Also:

emptyIfNull(List), emptyIfNull(Set), emptyIfNull(Map)

emptyIfNull

@Nonnull
public static <T> java.util.List<T> emptyIfNull(@Nullable
                                                java.util.List<T> list)

Safe wrapper around nullable list instances: returns list argument itself, if the list is non-null, otherwise returns (immutable) empty list.

Type Parameters:

T - list entities type

Parameters:

list - List instance to process

Returns:

original list instance, if non-null; otherwise immutable empty list instance.

See Also:

emptyIfNull(Collection), emptyIfNull(Set), emptyIfNull(Map)

emptyIfNull

@Nonnull
public static <T> java.util.Set<T> emptyIfNull(@Nullable
                                               java.util.Set<T> set)

Safe wrapper around nullable set instances: returns set argument itself, if the set is non-null, otherwise returns (immutable) empty set.

Type Parameters:

T - set entities type

Parameters:

set - Set instance to process

Returns:

original set instance, if non-null; otherwise immutable empty set instance.

See Also:

emptyIfNull(Collection), emptyIfNull(List), emptyIfNull(Map)

emptyIfNull

@Nonnull
public static <K,V> java.util.Map<K,V> emptyIfNull(@Nullable
                                                               java.util.Map<K,V> map)

Safe wrapper around nullable map instances: returns map argument itself, if the map is non-null, otherwise returns (immutable) empty map.

Type Parameters:

K - map key type

V - map value type

Parameters:

map - Map instance to process

Returns:

original map instance, if non-null; otherwise immutable empty map instance.

See Also:

emptyIfNull(Collection), emptyIfNull(List), emptyIfNull(Set)