org.apache.polygene.api.util

Class Collectors

java.lang.Object

org.apache.polygene.api.util.Collectors

public class Collectors
extends Object

Implementations of Collector missing from the JDK.

Method Summary

Modifier and Type	Method and Description
static <T> Collector<T,?,T>	single() Collect a single element.
static <T> Collector<T,?,Optional<T>>	singleOrEmpty() Eventually collect a single element.
static <T extends Map.Entry<K,U>,K,U> Collector<T,?,Map<K,U>>	toMap() Collect map entries into a HashMap.
static <T,K,U,M extends Map<K,U>> Collector<T,?,M>	toMap(Function<? super T,? extends K> keyMapper, Function<? super T,? extends U> valueMapper, Supplier<M> mapSupplier) Collect map entries into a map.
static <T extends Map.Entry<K,U>,K,U,M extends Map<K,U>> Collector<T,?,M>	toMap(Supplier<M> mapSupplier) Collect map entries into a map.
static <T extends Map.Entry<K,U>,K,U> Collector<T,?,Map<K,U>>	toMapWithNullValues() Collect map entries into a HashMap, allowing null values.
static <T,K,U,M extends Map<K,U>> Collector<T,?,M>	toMapWithNullValues(Function<? super T,? extends K> keyMapper, Function<? super T,? extends U> valueMapper, Supplier<M> mapSupplier) Collect map entries into a map, allowing null values.
static <T extends Map.Entry<K,U>,K,U,M extends Map<K,U>> Collector<T,?,M>	toMapWithNullValues(Supplier<M> mapSupplier) Collect map entries into a map, allowing null values.

Methods inherited from class java.lang.Object

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

Method Detail

single

public static <T> Collector<T,?,T> single()
                                   throws IllegalArgumentException

Collect a single element. The Collector throws IllegalArgumentException if no or more than one element.

Type Parameters:

T - Element type

Returns:

The single element collector

Throws:

IllegalArgumentException

singleOrEmpty

public static <T> Collector<T,?,Optional<T>> singleOrEmpty()

Eventually collect a single element. The Collector throws IllegalArgumentException if more than one element.

Type Parameters:

T - Element type

Returns:

The optional single element collector

toMap

public static <T extends Map.Entry<K,U>,K,U> Collector<T,?,Map<K,U>> toMap()

Collect map entries into a HashMap. The Collector throws NullPointerException if one entry has a null value. The Collector throws IllegalStateException if duplicate keys are found.

Type Parameters:

T - the Map entry type

K - the collected map key type

U - the collected map value type

Returns:

a Collector which collects elements into a Map

toMap

public static <T extends Map.Entry<K,U>,K,U,M extends Map<K,U>> Collector<T,?,M> toMap(Supplier<M> mapSupplier)

Collect map entries into a map. The Collector throws NullPointerException if one entry has a null value. The Collector throws IllegalStateException if duplicate keys are found.

Type Parameters:

M - the type of the resulting Map

T - the Map entry type

K - the collected map key type

U - the collected map value type

Parameters:

mapSupplier - a function which returns a new, empty Map into which the results will be inserted

Returns:

The map collector

toMap

public static <T,K,U,M extends Map<K,U>> Collector<T,?,M> toMap(Function<? super T,? extends K> keyMapper,
                                                                Function<? super T,? extends U> valueMapper,
                                                                Supplier<M> mapSupplier)

Collect map entries into a map. The Collector throws NullPointerException if one entry has a null value. The Collector throws IllegalStateException if duplicate keys are found.

Type Parameters:

M - the type of the resulting Map

T - the Map entry type

K - the collected map key type

U - the collected map value type

Parameters:

keyMapper - a mapping function to produce keys

valueMapper - a mapping function to produce values

mapSupplier - a function which returns a new, empty Map into which the results will be inserted

Returns:

The map collector

toMapWithNullValues

public static <T extends Map.Entry<K,U>,K,U> Collector<T,?,Map<K,U>> toMapWithNullValues()

Collect map entries into a HashMap, allowing null values. The Collector throws IllegalStateException if duplicate keys are found. See https://bugs.openjdk.java.net/browse/JDK-8148463

Type Parameters:

T - the Map entry type

K - the collected map key type

U - the collected map value type

Returns:

The map collector

toMapWithNullValues

public static <T extends Map.Entry<K,U>,K,U,M extends Map<K,U>> Collector<T,?,M> toMapWithNullValues(Supplier<M> mapSupplier)

Collect map entries into a map, allowing null values. The Collector throws IllegalStateException if duplicate keys are found. See https://bugs.openjdk.java.net/browse/JDK-8148463

Type Parameters:

M - the type of the resulting Map

T - the Map entry type

K - the collected map key type

U - the collected map value type

Parameters:

mapSupplier - a function which returns a new, empty Map into which the results will be inserted

Returns:

The map collector

toMapWithNullValues

public static <T,K,U,M extends Map<K,U>> Collector<T,?,M> toMapWithNullValues(Function<? super T,? extends K> keyMapper,
                                                                              Function<? super T,? extends U> valueMapper,
                                                                              Supplier<M> mapSupplier)

Collect map entries into a map, allowing null values. The Collector throws IllegalStateException if duplicate keys are found. See https://bugs.openjdk.java.net/browse/JDK-8148463

Type Parameters:

M - the type of the resulting Map

T - the Map entry type

K - the collected map key type

U - the collected map value type

Parameters:

keyMapper - a mapping function to produce keys

valueMapper - a mapping function to produce values

mapSupplier - a function which returns a new, empty Map into which the results will be inserted

Returns:

The map collector