/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You under the Apache License, Version 2.0
    * (the "License"); you may not use this file except in compliance with
    * the License.  You may obtain a copy of the License at
    *
    *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.commons.lang3.stream;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.Enumeration;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Objects;
  import java.util.Set;
  import java.util.Spliterator;
  import java.util.Spliterators;
  import java.util.Spliterators.AbstractSpliterator;
  import java.util.function.BiConsumer;
  import java.util.function.BinaryOperator;
  import java.util.function.Consumer;
  import java.util.function.Function;
  import java.util.function.Predicate;
  import java.util.function.Supplier;
  import java.util.stream.Collector;
  import java.util.stream.Collectors;
  import java.util.stream.Stream;
  import java.util.stream.StreamSupport;
  
  import org.apache.commons.lang3.ArrayUtils;
  import org.apache.commons.lang3.function.Failable;
  import org.apache.commons.lang3.function.FailableConsumer;
  import org.apache.commons.lang3.function.FailableFunction;
  import org.apache.commons.lang3.function.FailablePredicate;
  
  /**
   * Provides utility functions, and classes for working with the {@link java.util.stream} package, or more generally, with Java 8 lambdas. More specifically, it
   * attempts to address the fact that lambdas are supposed not to throw Exceptions, at least not checked Exceptions, AKA instances of {@link Exception}. This
   * enforces the use of constructs like:
   *
   * <pre>{@code
   * Consumer<java.lang.reflect.Method> consumer = m -> {
   *     try {
   *         m.invoke(o, args);
   *     } catch (Throwable t) {
   *         throw Failable.rethrow(t);
   *     }
   * };
   * stream.forEach(consumer);
   * }</pre>
   * <p>
   * Using a {@link FailableStream}, this can be rewritten as follows:
   * </p>
   *
   * <pre>{@code
   * Streams.failable(stream).forEach(m -> m.invoke(o, args));
   * }</pre>
   * <p>
   * Obviously, the second version is much more concise and the spirit of Lambda expressions is met better than in the first version.
   * </p>
   *
   * @see Stream
   * @see Failable
   * @since 3.11
   */
  public class Streams {
  
      /**
       * A Collector type for arrays.
       *
       * @param <E> The array type.
       */
      public static class ArrayCollector<E> implements Collector<E, List<E>, E[]> {
          private static final Set<Characteristics> characteristics = Collections.emptySet();
          private final Class<E> elementType;
  
          /**
           * Constructs a new instance for the given element type.
           *
           * @param elementType The element type.
           */
          public ArrayCollector(final Class<E> elementType) {
              this.elementType = Objects.requireNonNull(elementType, "elementType");
          }
  
          @Override
          public BiConsumer<List<E>, E> accumulator() {
              return List::add;
         }
 
         @Override
         public Set<Characteristics> characteristics() {
             return characteristics;
         }
 
         @Override
         public BinaryOperator<List<E>> combiner() {
             return (left, right) -> {
                 left.addAll(right);
                 return left;
             };
         }
 
         @Override
         public Function<List<E>, E[]> finisher() {
             return list -> list.toArray(ArrayUtils.newInstance(elementType, list.size()));
         }
 
         @Override
         public Supplier<List<E>> supplier() {
             return ArrayList::new;
         }
     }
 
     /**
      * Helps implement {@link Streams#of(Enumeration)}.
      *
      * @param <T> The element type.
      */
     private static final class EnumerationSpliterator<T> extends AbstractSpliterator<T> {
 
         private final Enumeration<T> enumeration;
 
         /**
          * Creates a spliterator reporting the given estimated size and additionalCharacteristics.
          *
          * @param estimatedSize the estimated size of this spliterator if known, otherwise {@code Long.MAX_VALUE}.
          * @param additionalCharacteristics properties of this spliterator's source or elements. If {@code SIZED} is reported then this spliterator will
          *        additionally report {@code SUBSIZED}.
          * @param enumeration The Enumeration to wrap.
          */
         protected EnumerationSpliterator(final long estimatedSize, final int additionalCharacteristics, final Enumeration<T> enumeration) {
             super(estimatedSize, additionalCharacteristics);
             this.enumeration = Objects.requireNonNull(enumeration, "enumeration");
         }
 
         @Override
         public void forEachRemaining(final Consumer<? super T> action) {
             while (enumeration.hasMoreElements()) {
                 next(action);
             }
         }
 
         private boolean next(final Consumer<? super T> action) {
             action.accept(enumeration.nextElement());
             return true;
 
         }
 
         @Override
         public boolean tryAdvance(final Consumer<? super T> action) {
             return enumeration.hasMoreElements() && next(action);
         }
     }
 
     /**
      * A reduced, and simplified version of a {@link Stream} with failable method signatures.
      *
      * @param <T> The streams element type.
      */
     public static class FailableStream<T> {
 
         private Stream<T> stream;
         private boolean terminated;
 
         /**
          * Constructs a new instance with the given {@code stream}.
          *
          * @param stream The stream.
          */
         public FailableStream(final Stream<T> stream) {
             this.stream = stream;
         }
 
         /**
          * Returns whether all elements of this stream match the provided predicate. May not evaluate the predicate on all
          * elements if not necessary for determining the result. If the stream is empty then {@code true} is returned and the
          * predicate is not evaluated.
          *
          * <p>
          * This is a short-circuiting terminal operation.
          * </p>
          *
          * Note This method evaluates the <em>universal quantification</em> of the predicate over the elements of the stream
          * (for all x P(x)). If the stream is empty, the quantification is said to be <em>vacuously satisfied</em> and is always
          * {@code true} (regardless of P(x)).
          *
          * @param predicate A non-interfering, stateless predicate to apply to elements of this stream
          * @return {@code true} If either all elements of the stream match the provided predicate or the stream is empty,
          *         otherwise {@code false}.
          */
         public boolean allMatch(final FailablePredicate<T, ?> predicate) {
             assertNotTerminated();
             return stream().allMatch(Failable.asPredicate(predicate));
         }
 
         /**
          * Returns whether any elements of this stream match the provided predicate. May not evaluate the predicate on all
          * elements if not necessary for determining the result. If the stream is empty then {@code false} is returned and the
          * predicate is not evaluated.
          *
          * <p>
          * This is a short-circuiting terminal operation.
          * </p>
          *
          * Note This method evaluates the <em>existential quantification</em> of the predicate over the elements of the stream
          * (for some x P(x)).
          *
          * @param predicate A non-interfering, stateless predicate to apply to elements of this stream
          * @return {@code true} if any elements of the stream match the provided predicate, otherwise {@code false}
          */
         public boolean anyMatch(final FailablePredicate<T, ?> predicate) {
             assertNotTerminated();
             return stream().anyMatch(Failable.asPredicate(predicate));
         }
 
         /**
          * Throws IllegalStateException if this stream is already terminated.
          *
          * @throws IllegalStateException if this stream is already terminated.
          */
         protected void assertNotTerminated() {
             if (terminated) {
                 throw new IllegalStateException("This stream is already terminated.");
             }
         }
 
         /**
          * Performs a mutable reduction operation on the elements of this stream using a {@link Collector}. A {@link Collector}
          * encapsulates the functions used as arguments to {@link #collect(Supplier, BiConsumer, BiConsumer)}, allowing for
          * reuse of collection strategies and composition of collect operations such as multiple-level grouping or partitioning.
          *
          * <p>
          * If the underlying stream is parallel, and the {@link Collector} is concurrent, and either the stream is unordered or
          * the collector is unordered, then a concurrent reduction will be performed (see {@link Collector} for details on
          * concurrent reduction.)
          * </p>
          *
          * <p>
          * This is a terminal operation.
          * </p>
          *
          * <p>
          * When executed in parallel, multiple intermediate results may be instantiated, populated, and merged so as to maintain
          * isolation of mutable data structures. Therefore, even when executed in parallel with non-thread-safe data structures
          * (such as {@link ArrayList}), no additional synchronization is needed for a parallel reduction.
          * </p>
          *
          * Note The following will accumulate strings into an ArrayList:
          *
          * <pre>
          * {@code
          *     List<String> asList = stringStream.collect(Collectors.toList());
          * }
          * </pre>
          *
          * <p>
          * The following will classify {@code Person} objects by city:
          * </p>
          *
          * <pre>
          * {@code
          *     Map<String, List<Person>> peopleByCity = personStream.collect(Collectors.groupingBy(Person::getCity));
          * }
          * </pre>
          *
          * <p>
          * The following will classify {@code Person} objects by state and city, cascading two {@link Collector}s together:
          * </p>
          *
          * <pre>
          * {@code
          *     Map<String, Map<String, List<Person>>> peopleByStateAndCity = personStream
          *         .collect(Collectors.groupingBy(Person::getState, Collectors.groupingBy(Person::getCity)));
          * }
          * </pre>
          *
          * @param <R> the type of the result
          * @param <A> the intermediate accumulation type of the {@link Collector}
          * @param collector the {@link Collector} describing the reduction
          * @return the result of the reduction
          * @see #collect(Supplier, BiConsumer, BiConsumer)
          * @see Collectors
          */
         public <A, R> R collect(final Collector<? super T, A, R> collector) {
             makeTerminated();
             return stream().collect(collector);
         }
 
         /**
          * Performs a mutable reduction operation on the elements of this FailableStream. A mutable reduction is one in which
          * the reduced value is a mutable result container, such as an {@link ArrayList}, and elements are incorporated by
          * updating the state of the result rather than by replacing the result. This produces a result equivalent to:
          * <pre>
          * {@code
          *     R result = supplier.get();
          *     for (T element : this stream)
          *         accumulator.accept(result, element);
          *     return result;
          * }
          * </pre>
          * <p>
          * Like {@link #reduce(Object, BinaryOperator)}, {@code collect} operations can be parallelized without requiring
          * additional synchronization.
          * </p>
          * <p>
          * This is a terminal operation.
          * </p>
          * <p>
          * Note There are many existing classes in the JDK whose signatures are well-suited for use with method references as
          * arguments to {@code collect()}. For example, the following will accumulate strings into an {@link ArrayList}:
          * </p>
          * <pre>
          * {@code
          *     List<String> asList = stringStream.collect(ArrayList::new, ArrayList::add, ArrayList::addAll);
          * }
          * </pre>
          * <p>
          * The following will take a stream of strings and concatenates them into a single string:
          * </p>
          * <pre>
          * {@code
          *     String concat = stringStream.collect(StringBuilder::new, StringBuilder::append, StringBuilder::append).toString();
          * }
          * </pre>
          *
          * @param <R> type of the result
          * @param <A> Type of the accumulator.
          * @param supplier a function that creates a new result container. For a parallel execution, this function may be called
          *        multiple times and must return a fresh value each time.
          * @param accumulator An associative, non-interfering, stateless function for incorporating an additional element into a
          *        result
          * @param combiner An associative, non-interfering, stateless function for combining two values, which must be
          *        compatible with the accumulator function
          * @return The result of the reduction
          */
         public <A, R> R collect(final Supplier<R> supplier, final BiConsumer<R, ? super T> accumulator, final BiConsumer<R, R> combiner) {
             makeTerminated();
             return stream().collect(supplier, accumulator, combiner);
         }
 
         /**
          * Returns a FailableStream consisting of the elements of this stream that match the given FailablePredicate.
          * <p>
          * This is an intermediate operation.
          * </p>
          *
          * @param predicate a non-interfering, stateless predicate to apply to each element to determine if it should be
          *        included.
          * @return the new stream
          */
         public FailableStream<T> filter(final FailablePredicate<T, ?> predicate) {
             assertNotTerminated();
             stream = stream.filter(Failable.asPredicate(predicate));
             return this;
         }
 
         /**
          * Performs an action for each element of this stream.
          * <p>
          * This is a terminal operation.
          * </p>
          * <p>
          * The behavior of this operation is explicitly nondeterministic. For parallel stream pipelines, this operation does
          * <em>not</em> guarantee to respect the encounter order of the stream, as doing so would sacrifice the benefit of
          * parallelism. For any given element, the action may be performed at whatever time and in whatever thread the library
          * chooses. If the action accesses shared state, it is responsible for providing the required synchronization.
          * </p>
          *
          * @param action a non-interfering action to perform on the elements
          */
         public void forEach(final FailableConsumer<T, ?> action) {
             makeTerminated();
             stream().forEach(Failable.asConsumer(action));
         }
 
         /**
          * Marks this stream as terminated.
          *
          * @throws IllegalStateException if this stream is already terminated.
          */
         protected void makeTerminated() {
             assertNotTerminated();
             terminated = true;
         }
 
         /**
          * Returns a stream consisting of the results of applying the given function to the elements of this stream.
          *
          * <p>
          * This is an intermediate operation.
          * </p>
          *
          * @param <R> The element type of the new stream
          * @param mapper A non-interfering, stateless function to apply to each element
          * @return the new stream
          */
         public <R> FailableStream<R> map(final FailableFunction<T, R, ?> mapper) {
             assertNotTerminated();
             return new FailableStream<>(stream.map(Failable.asFunction(mapper)));
         }
 
         /**
          * Performs a reduction on the elements of this stream, using the provided identity value and an associative
          * accumulation function, and returns the reduced value. This is equivalent to:
          *
          * <pre>
          * {@code
          *     T result = identity;
          *     for (T element : this stream)
          *         result = accumulator.apply(result, element)
          *     return result;
          * }
          * </pre>
          *
          * but is not constrained to execute sequentially.
          *
          * <p>
          * The {@code identity} value must be an identity for the accumulator function. This means that for all {@code t},
          * {@code accumulator.apply(identity, t)} is equal to {@code t}. The {@code accumulator} function must be an associative
          * function.
          * </p>
          *
          * <p>
          * This is a terminal operation.
          * </p>
          *
          * Note Sum, min, max, average, and string concatenation are all special cases of reduction. Summing a stream of numbers
          * can be expressed as:
          *
          * <pre>
          * {@code
          *     Integer sum = integers.reduce(0, (a, b) -> a + b);
          * }
          * </pre>
          *
          * or:
          *
          * <pre>
          * {@code
          *     Integer sum = integers.reduce(0, Integer::sum);
          * }
          * </pre>
          *
          * <p>
          * While this may seem a more roundabout way to perform an aggregation compared to simply mutating a running total in a
          * loop, reduction operations parallelize more gracefully, without needing additional synchronization and with greatly
          * reduced risk of data races.
          * </p>
          *
          * @param identity the identity value for the accumulating function
          * @param accumulator an associative, non-interfering, stateless function for combining two values
          * @return the result of the reduction
          */
         public T reduce(final T identity, final BinaryOperator<T> accumulator) {
             makeTerminated();
             return stream().reduce(identity, accumulator);
         }
 
         /**
          * Converts the FailableStream into an equivalent stream.
          *
          * @return A stream, which will return the same elements, which this FailableStream would return.
          */
         public Stream<T> stream() {
             return stream;
         }
     }
 
     /**
      * Converts the given {@link Collection} into a {@link FailableStream}. This is basically a simplified, reduced version
      * of the {@link Stream} class, with the same underlying element stream, except that failable objects, like
      * {@link FailablePredicate}, {@link FailableFunction}, or {@link FailableConsumer} may be applied, instead of
      * {@link Predicate}, {@link Function}, or {@link Consumer}. The idea is to rewrite a code snippet like this:
      *
      * <pre>
      * {@code
      * final List<O> list;
      * final Method m;
      * final Function<O, String> mapper = (o) -> {
      *     try {
      *         return (String) m.invoke(o);
      *     } catch (Throwable t) {
      *         throw Failable.rethrow(t);
      *     }
      * };
      * final List<String> strList = list.stream().map(mapper).collect(Collectors.toList());
      * }
      * </pre>
      *
      * as follows:
      *
      * <pre>
      * {@code
      * final List<O> list;
      * final Method m;
      * final List<String> strList = Failable.stream(list.stream()).map((o) -> (String) m.invoke(o)).collect(Collectors.toList());
      * }
      * </pre>
      *
      * While the second version may not be <em>quite</em> as efficient (because it depends on the creation of additional,
      * intermediate objects, of type FailableStream), it is much more concise, and readable, and meets the spirit of Lambdas
      * better than the first version.
      *
      * @param <T> The streams element type.
      * @param stream The stream, which is being converted.
      * @return The {@link FailableStream}, which has been created by converting the stream.
      * @since 3.13.0
      */
     public static <T> FailableStream<T> failableStream(final Collection<T> stream) {
         return failableStream(of(stream));
     }
 
     /**
      * Converts the given {@link Stream stream} into a {@link FailableStream}. This is basically a simplified, reduced
      * version of the {@link Stream} class, with the same underlying element stream, except that failable objects, like
      * {@link FailablePredicate}, {@link FailableFunction}, or {@link FailableConsumer} may be applied, instead of
      * {@link Predicate}, {@link Function}, or {@link Consumer}. The idea is to rewrite a code snippet like this:
      *
      * <pre>
      * {@code
      * final List<O> list;
      * final Method m;
      * final Function<O, String> mapper = (o) -> {
      *     try {
      *         return (String) m.invoke(o);
      *     } catch (Throwable t) {
      *         throw Failable.rethrow(t);
      *     }
      * };
      * final List<String> strList = list.stream().map(mapper).collect(Collectors.toList());
      * }
      * </pre>
      *
      * as follows:
      *
      * <pre>
      * {@code
      * final List<O> list;
      * final Method m;
      * final List<String> strList = Failable.stream(list.stream()).map((o) -> (String) m.invoke(o)).collect(Collectors.toList());
      * }
      * </pre>
      *
      * While the second version may not be <em>quite</em> as efficient (because it depends on the creation of additional,
      * intermediate objects, of type FailableStream), it is much more concise, and readable, and meets the spirit of Lambdas
      * better than the first version.
      *
      * @param <T> The streams element type.
      * @param stream The stream, which is being converted.
      * @return The {@link FailableStream}, which has been created by converting the stream.
      * @since 3.13.0
      */
     public static <T> FailableStream<T> failableStream(final Stream<T> stream) {
         return new FailableStream<>(stream);
     }
 
     /**
      * Shorthand for {@code Streams.failableStream(value == null ? Stream.empty() : Stream.of(value))}.
      *
      * @param <T> the type of stream elements.
      * @param value the single element of the new stream, may be {@code null}.
      * @return the new FailableStream on {@code value} or an empty stream.
      * @since 3.15.0
      */
     public static <T> FailableStream<T> failableStream(final T value) {
         return failableStream(streamOf(value));
     }
 
     /**
      * Shorthand for {@code Streams.failableStream(Streams.of(arrayValues))}.
      *
      * @param <T> the type of stream elements.
      * @param values the elements of the new stream, may be {@code null}.
      * @return the new FailableStream on {@code values} or an empty stream.
      * @since 3.14.0
      */
     @SafeVarargs // Creating a stream from an array is safe
     public static <T> FailableStream<T> failableStream(final T... values) {
         return failableStream(of(values));
     }
 
     /**
      * Streams only instances of the give Class in a collection.
      * <p>
      * This method shorthand for:
      * </p>
      * <pre>
      * {@code (Stream<E>) Streams.toStream(collection).filter(collection, SomeClass.class::isInstance);}
      * </pre>
      *
      * @param <E> the type of elements in the collection we want to stream.
      * @param clazz the type of elements in the collection we want to stream.
      * @param collection the collection to stream or null.
      * @return A non-null stream that only provides instances we want.
      * @since 3.13.0
      */
     public static <E> Stream<E> instancesOf(final Class<? super E> clazz, final Collection<? super E> collection) {
         return instancesOf(clazz, of(collection));
     }
 
     @SuppressWarnings("unchecked") // After the isInstance check, we still need to type-cast.
     private static <E> Stream<E> instancesOf(final Class<? super E> clazz, final Stream<?> stream) {
         return (Stream<E>) of(stream).filter(clazz::isInstance);
     }
 
     /**
      * Streams the non-null elements of a collection.
      *
      * @param <E> the type of elements in the collection.
      * @param collection the collection to stream or null.
      * @return A non-null stream that filters out null elements.
      * @since 3.13.0
      */
     public static <E> Stream<E> nonNull(final Collection<E> collection) {
         return of(collection).filter(Objects::nonNull);
     }
 
     /**
      * Streams the non-null element.
      *
      * @param <E> the type of elements in the collection.
      * @param array the element to stream or null.
      * @return A non-null stream that filters out a null element.
      * @since 3.15.0
      */
     public static <E> Stream<E> nonNull(final E array) {
         return nonNull(streamOf(array));
     }
 
     /**
      * Streams the non-null elements of an array.
      *
      * @param <E> the type of elements in the collection.
      * @param array the array to stream or null.
      * @return A non-null stream that filters out null elements.
      * @since 3.13.0
      */
     @SafeVarargs
     public static <E> Stream<E> nonNull(final E... array) {
         return nonNull(of(array));
     }
 
     /**
      * Streams the non-null elements of a stream.
      *
      * @param <E> the type of elements in the collection.
      * @param stream the stream to stream or null.
      * @return A non-null stream that filters out null elements.
      * @since 3.13.0
      */
     public static <E> Stream<E> nonNull(final Stream<E> stream) {
         return of(stream).filter(Objects::nonNull);
     }
 
     /**
      * Delegates to {@link Collection#stream()} or returns {@link Stream#empty()} if the collection is null.
      *
      * @param <E> the type of elements in the collection.
      * @param collection the collection to stream or null.
      * @return {@link Collection#stream()} or {@link Stream#empty()} if the collection is null.
      * @since 3.13.0
      */
     public static <E> Stream<E> of(final Collection<E> collection) {
         return collection == null ? Stream.empty() : collection.stream();
     }
 
     /**
      * Streams the elements of the given enumeration in order.
      *
      * @param <E> The enumeration element type.
      * @param enumeration The enumeration to stream.
      * @return a new stream.
      * @since 3.13.0
      */
     public static <E> Stream<E> of(final Enumeration<E> enumeration) {
         return StreamSupport.stream(new EnumerationSpliterator<>(Long.MAX_VALUE, Spliterator.ORDERED, enumeration), false);
     }
 
     /**
      * Creates a stream on the given Iterable.
      *
      * @param <E> the type of elements in the Iterable.
      * @param iterable the Iterable to stream or null.
      * @return a new Stream or {@link Stream#empty()} if the Iterable is null.
      * @since 3.13.0
      */
     public static <E> Stream<E> of(final Iterable<E> iterable) {
         return iterable == null ? Stream.empty() : StreamSupport.stream(iterable.spliterator(), false);
     }
 
     /**
      * Creates a stream on the given Iterator.
      *
      * @param <E> the type of elements in the Iterator.
      * @param iterator the Iterator to stream or null.
      * @return a new Stream or {@link Stream#empty()} if the Iterator is null.
      * @since 3.13.0
      */
     public static <E> Stream<E> of(final Iterator<E> iterator) {
         return iterator == null ? Stream.empty() : StreamSupport.stream(Spliterators.spliteratorUnknownSize(iterator, Spliterator.ORDERED), false);
     }
 
     /**
      * Returns the stream or {@link Stream#empty()} if the stream is null.
      *
      * @param <E> the type of elements in the collection.
      * @param stream the stream to stream or null.
      * @return the stream or {@link Stream#empty()} if the stream is null.
      * @since 3.13.0
      */
     private static <E> Stream<E> of(final Stream<E> stream) {
         return stream == null ? Stream.empty() : stream;
     }
 
     /**
      * Null-safe version of {@link Stream#of(Object[])}.
      *
      * @param <T> the type of stream elements.
      * @param values the elements of the new stream, may be {@code null}.
      * @return the new stream on {@code values} or {@link Stream#empty()}.
      * @since 3.13.0
      */
     @SafeVarargs // Creating a stream from an array is safe
     public static <T> Stream<T> of(final T... values) {
         return values == null ? Stream.empty() : Stream.of(values);
     }
 
     /**
      * Converts the given {@link Collection} into a {@link FailableStream}. This is basically a simplified, reduced version
      * of the {@link Stream} class, with the same underlying element stream, except that failable objects, like
      * {@link FailablePredicate}, {@link FailableFunction}, or {@link FailableConsumer} may be applied, instead of
      * {@link Predicate}, {@link Function}, or {@link Consumer}. The idea is to rewrite a code snippet like this:
      *
      * <pre>
      * {@code
      * final List<O> list;
      * final Method m;
      * final Function<O, String> mapper = (o) -> {
      *     try {
      *         return (String) m.invoke(o);
      *     } catch (Throwable t) {
      *         throw Failable.rethrow(t);
      *     }
      * };
      * final List<String> strList = list.stream().map(mapper).collect(Collectors.toList());
      * }
      * </pre>
      *
      * as follows:
      *
      * <pre>
      * {@code
      * final List<O> list;
      * final Method m;
      * final List<String> strList = Failable.stream(list.stream()).map((o) -> (String) m.invoke(o)).collect(Collectors.toList());
      * }
      * </pre>
      *
      * While the second version may not be <em>quite</em> as efficient (because it depends on the creation of additional,
      * intermediate objects, of type FailableStream), it is much more concise, and readable, and meets the spirit of Lambdas
      * better than the first version.
      *
      * @param <E> The streams element type.
      * @param collection The stream, which is being converted.
      * @return The {@link FailableStream}, which has been created by converting the stream.
      * @deprecated Use {@link #failableStream(Collection)}.
      */
     @Deprecated
     public static <E> FailableStream<E> stream(final Collection<E> collection) {
         return failableStream(collection);
     }
 
     /**
      * Converts the given {@link Stream stream} into a {@link FailableStream}. This is basically a simplified, reduced
      * version of the {@link Stream} class, with the same underlying element stream, except that failable objects, like
      * {@link FailablePredicate}, {@link FailableFunction}, or {@link FailableConsumer} may be applied, instead of
      * {@link Predicate}, {@link Function}, or {@link Consumer}. The idea is to rewrite a code snippet like this:
      *
      * <pre>
      * {@code
      * final List<O> list;
      * final Method m;
      * final Function<O, String> mapper = (o) -> {
      *     try {
      *         return (String) m.invoke(o);
      *     } catch (Throwable t) {
      *         throw Failable.rethrow(t);
      *     }
      * };
      * final List<String> strList = list.stream().map(mapper).collect(Collectors.toList());
      * }
      * </pre>
      *
      * as follows:
      *
      * <pre>
      * {@code
      * final List<O> list;
      * final Method m;
      * final List<String> strList = Failable.stream(list.stream()).map((o) -> (String) m.invoke(o)).collect(Collectors.toList());
      * }
      * </pre>
      *
      * While the second version may not be <em>quite</em> as efficient (because it depends on the creation of additional,
      * intermediate objects, of type FailableStream), it is much more concise, and readable, and meets the spirit of Lambdas
      * better than the first version.
      *
      * @param <T> The streams element type.
      * @param stream The stream, which is being converted.
      * @return The {@link FailableStream}, which has been created by converting the stream.
      * @deprecated Use {@link #failableStream(Stream)}.
      */
     @Deprecated
     public static <T> FailableStream<T> stream(final Stream<T> stream) {
         return failableStream(stream);
     }
 
     private static <T> Stream<T> streamOf(final T value) {
         return value == null ? Stream.empty() : Stream.of(value);
     }
 
     /**
      * Returns a {@link Collector} that accumulates the input elements into a new array.
      *
      * @param elementType Type of an element in the array.
      * @param <T> the type of the input elements
      * @return a {@link Collector} which collects all the input elements into an array, in encounter order
      */
     public static <T> Collector<T, ?, T[]> toArray(final Class<T> elementType) {
         return new ArrayCollector<>(elementType);
     }
 
     /**
      * Constructs a new instance.
      *
      * @deprecated Will be private in 4.0.0.
      */
     @Deprecated
     public Streams() {
         // empty
     }
 }