Example usage for java.util.stream Collector of

List of usage examples for java.util.stream Collector of

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Introduction

In this page you can find the example usage for java.util.stream Collector of.

Prototype

public static <T, A, R> Collector<T, A, R> of(Supplier<A> supplier, BiConsumer<A, T> accumulator,
        BinaryOperator<A> combiner, Function<A, R> finisher, Characteristics... characteristics)

Source Link

Document

Returns a new Collector described by the given supplier , accumulator , combiner , and finisher functions.

Usage

From source file:Main.java

public static <E> Collector<E, ImmutableList.Builder<E>, ImmutableList<E>> collectToImmutableList() {
    return Collector.of(
            ImmutableList::builder, ImmutableList.Builder::add, (ImmutableList.Builder<E> builder1,
                    ImmutableList.Builder<E> builder2) -> builder1.addAll(builder2.build()),
            ImmutableList.Builder::build, Characteristics.CONCURRENT);
}

From source file:com.ikanow.aleph2.shared.crud.mongodb.utils.MongoDbUtils.java

/** Creates a big $and/$or list of the list of "multi query components"
 * @param andVsOr - top level MongoDB operator
 * @param query_in - a multi query//  w w  w. j ava2s.  com
 * @return the MongoDB query object (no meta - that is added above)
 */
@SuppressWarnings("unchecked")
protected static <T> DBObject convertToMongoQuery_multi(final String andVsOr,
        final MultiQueryComponent<T> query_in) {

    return Patterns.match(query_in.getElements()).<DBObject>andReturn()
            .when(f -> f.isEmpty(), f -> new BasicDBObject())
            .otherwise(f -> f.stream().collect(Collector.of(BasicDBList::new, (acc, entry) -> {
                Patterns.match(entry).andAct()
                        .when(SingleQueryComponent.class,
                                e -> acc.add(convertToMongoQuery_single(getOperatorName(e.getOp()), e)))
                        .when(MultiQueryComponent.class,
                                e -> acc.add(convertToMongoQuery_multi(
                                        getOperatorName(((MultiQueryComponent<?>) e).getOp()),
                                        (MultiQueryComponent<?>) e)));
                //(at various other points in the code, oraclej has complained about this though ecj is happy, so just added these casts for safety)
            }, (a, b) -> {
                a.addAll(b);
                return a;
            }, acc -> (DBObject) new BasicDBObject(andVsOr, acc), Characteristics.UNORDERED)));
}

From source file:com.ikanow.aleph2.data_model.utils.TestCrudUtils.java

@SuppressWarnings("unchecked")
protected static <T> DBObject convertToMongoQuery_multi(final String andVsOr,
        final MultiQueryComponent<T> query_in) {

    return Patterns.match(query_in.getElements()).<DBObject>andReturn()
            .when(f -> f.isEmpty(), f -> new BasicDBObject())
            .otherwise(f -> f.stream().collect(Collector.of(BasicDBList::new, (acc, entry) -> {
                Patterns.match(entry).andAct()
                        .when(SingleQueryComponent.class,
                                e -> acc.add(convertToMongoQuery_single(getOperatorName(e.getOp()), e)))
                        .when(MultiQueryComponent.class,
                                e -> acc.add(convertToMongoQuery_multi(
                                        getOperatorName(((MultiQueryComponent<?>) e).getOp()),
                                        (MultiQueryComponent<?>) e)));
                //(at various other points in the code, oraclej has complained about this though ecj is happy, so just added these casts for safety)
            }, (a, b) -> {/*from w  w  w . ja  va 2  s  . c  o m*/
                a.addAll(b);
                return a;
            }, acc -> (DBObject) new BasicDBObject(andVsOr, acc), Characteristics.UNORDERED)));
}

From source file:com.github.steveash.guavate.Guavate.java

/**
 * Collector used at the end of a stream to build an immutable set.
 * <p>//from  w  ww  .  jav  a2  s . c o m
 * A collector is used to gather data at the end of a stream operation.
 * This method returns a collector allowing streams to be gathered into
 * an {@link ImmutableSet}.
 * @param <T> the type of element in the set
 * @return the immutable set collector
 */
public static <T> Collector<T, ImmutableSet.Builder<T>, ImmutableSet<T>> toImmutableSet() {
    return Collector.of(ImmutableSet.Builder<T>::new, ImmutableSet.Builder<T>::add,
            (l, r) -> l.addAll(r.build()), ImmutableSet.Builder<T>::build, Collector.Characteristics.UNORDERED);
}

From source file:com.github.steveash.guavate.Guavate.java

/**
 * Collector used at the end of a stream to build an immutable sorted set.
 * <p>//w  w  w.j  a v  a  2  s .  com
 * A collector is used to gather data at the end of a stream operation.
 * This method returns a collector allowing streams to be gathered into
 * an {@link ImmutableSet}.
 * @param <T> the type of element in the sorted set
 * @return the immutable sorted set collector
 */
public static <T extends Comparable<?>> Collector<T, ImmutableSortedSet.Builder<T>, ImmutableSortedSet<T>> toImmutableSortedSet() {
    return Collector.of((Supplier<ImmutableSortedSet.Builder<T>>) ImmutableSortedSet::naturalOrder,
            ImmutableSortedSet.Builder<T>::add, (l, r) -> l.addAll(r.build()),
            ImmutableSortedSet.Builder<T>::build, Collector.Characteristics.UNORDERED);
}

From source file:com.github.steveash.guavate.Guavate.java

/**
 * Collector used at the end of a stream to build an immutable sorted set.
 * <p>//from www.ja v a2 s .  co  m
 * A collector is used to gather data at the end of a stream operation.
 * This method returns a collector allowing streams to be gathered into
 * an {@link ImmutableSet}.
 * @param <T> the type of element in the sorted set
 * @param comparator the comparator
 * @return the immutable sorted set collector
 */
public static <T> Collector<T, ImmutableSortedSet.Builder<T>, ImmutableSortedSet<T>> toImmutableSortedSet(
        Comparator<? super T> comparator) {
    return Collector.of(
            (Supplier<ImmutableSortedSet.Builder<T>>) () -> new ImmutableSortedSet.Builder<>(comparator),
            ImmutableSortedSet.Builder<T>::add, (l, r) -> l.addAll(r.build()),
            ImmutableSortedSet.Builder<T>::build, Collector.Characteristics.UNORDERED);
}

From source file:com.github.steveash.guavate.Guavate.java

/**
 * Collector used at the end of a stream to build an immutable multiset.
 * <p>//  ww  w.j a  va  2s .c  o m
 * A collector is used to gather data at the end of a stream operation.
 * This method returns a collector allowing streams to be gathered into
 * an {@link ImmutableMultiset}.
 * @param <T> the type of element in the multiset
 * @return the immutable multiset collector
 */
public static <T> Collector<T, ImmutableMultiset.Builder<T>, ImmutableMultiset<T>> toImmutableMultiset() {
    return Collector.of(ImmutableMultiset.Builder<T>::new, ImmutableMultiset.Builder<T>::add,
            (l, r) -> l.addAll(r.build()), ImmutableMultiset.Builder<T>::build,
            Collector.Characteristics.UNORDERED);
}

From source file:com.github.steveash.guavate.Guavate.java

/**
 * Collector used at the end of a stream to build an immutable map.
 * <p>//  w  ww  . j  a va2 s  . co m
 * A collector is used to gather data at the end of a stream operation.
 * This method returns a collector allowing streams to be gathered into
 * an {@link ImmutableMap}.
 * <p>
 * This returns a map by converting each stream element to a key and value.
 * The input stream must resolve to unique keys.
 * See {@link Collectors#toMap(Function, Function)} for more details.
 * @param <T> the type of the stream elements
 * @param <K> the type of the keys in the result map
 * @param <V> the type of the values in the result map
 * @param keyExtractor function to produce keys from stream elements
 * @param valueExtractor function to produce values from stream elements
 * @return the immutable map collector
 * @throws IllegalArgumentException if the same key is generated twice
 */
public static <T, K, V> Collector<T, ?, ImmutableMap<K, V>> toImmutableMap(
        Function<? super T, ? extends K> keyExtractor, Function<? super T, ? extends V> valueExtractor) {

    return Collector.of(ImmutableMap.Builder<K, V>::new,
            (builder, val) -> builder.put(keyExtractor.apply(val), valueExtractor.apply(val)),
            (l, r) -> l.putAll(r.build()), ImmutableMap.Builder<K, V>::build,
            Collector.Characteristics.UNORDERED);
}

From source file:com.github.steveash.guavate.Guavate.java

/**
 * Collector used at the end of a stream to build an immutable map.
 * <p>// w w w  .j a  v a 2 s  .com
 * A collector is used to gather data at the end of a stream operation.
 * This method returns a collector allowing streams to be gathered into
 * an {@link ImmutableMap}.
 * <p>
 * This returns a map by converting each stream element to a key and value.
 * If the same key is generated more than once the merge function is applied to the
 * values and the return value of the function is used as the value in the map.
 * @param <T> the type of the stream elements
 * @param <K> the type of the keys in the result map
 * @param <V> the type of the values in the result map
 * @param keyExtractor function to produce keys from stream elements
 * @param valueExtractor function to produce values from stream elements
 * @param mergeFn function to merge values with the same key
 * @return the immutable map collector
 */
public static <T, K, V> Collector<T, Map<K, V>, ImmutableMap<K, V>> toImmutableMap(
        Function<? super T, ? extends K> keyExtractor, Function<? super T, ? extends V> valueExtractor,
        BiFunction<? super V, ? super V, ? extends V> mergeFn) {

    return Collector.of(HashMap<K, V>::new,
            (map, val) -> map.merge(keyExtractor.apply(val), valueExtractor.apply(val), mergeFn),
            (m1, m2) -> mergeMaps(m1, m2, mergeFn), map -> ImmutableMap.copyOf(map),
            Collector.Characteristics.UNORDERED);
}

From source file:com.github.steveash.guavate.Guavate.java

/**
 * Collector used at the end of a stream to build an immutable sorted map.
 * <p>/*ww  w . j  av  a  2 s .c o m*/
 * A collector is used to gather data at the end of a stream operation.
 * This method returns a collector allowing streams to be gathered into
 * an {@link ImmutableSortedMap}.
 * <p>
 * This returns a map by converting each stream element to a key and value.
 * The input stream must resolve to unique keys.
 * See {@link Collectors#toMap(Function, Function)} for more details.
 * @param <T> the type of the stream elements
 * @param <K> the type of the keys in the result map
 * @param <V> the type of the values in the result map
 * @param keyExtractor function to produce keys from stream elements
 * @param valueExtractor function to produce values from stream elements
 * @return the immutable sorted map collector
 * @throws IllegalArgumentException if the same key is generated twice
 */
public static <T, K extends Comparable<?>, V> Collector<T, ?, ImmutableSortedMap<K, V>> toImmutableSortedMap(
        Function<? super T, ? extends K> keyExtractor, Function<? super T, ? extends V> valueExtractor) {

    return Collector.of((Supplier<ImmutableSortedMap.Builder<K, V>>) ImmutableSortedMap::naturalOrder,
            (builder, val) -> builder.put(keyExtractor.apply(val), valueExtractor.apply(val)),
            (l, r) -> l.putAll(r.build()), ImmutableSortedMap.Builder<K, V>::build,
            Collector.Characteristics.UNORDERED);
}