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Format new class.

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Gary Gregory 2020-07-10 11:47:45 -04:00
parent 1fc15b43d4
commit 265b74aac7
1 changed files with 398 additions and 380 deletions
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src/main/java/org/apache/commons/lang3/stream/Streams.java
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@ -66,425 +66,443 @@
*/
public class Streams {
public static class ArrayCollector<O> implements Collector<O, List<O>, O[]> {
private static final Set<Characteristics> characteristics = Collections.emptySet();
private final Class<O> elementType;
public static class ArrayCollector<O> implements Collector<O, List<O>, O[]> {
private static final Set<Characteristics> characteristics = Collections.emptySet();
private final Class<O> elementType;
public ArrayCollector(final Class<O> elementType) {
this.elementType = elementType;
}
public ArrayCollector(final Class<O> elementType) {
this.elementType = elementType;
}
@Override
public BiConsumer<List<O>, O> accumulator() {
return List::add;
}
@Override
public BiConsumer<List<O>, O> accumulator() {
return List::add;
}
@Override
public Set<Characteristics> characteristics() {
return characteristics;
}
@Override
public Set<Characteristics> characteristics() {
return characteristics;
}
@Override
public BinaryOperator<List<O>> combiner() {
return (left, right) -> {
left.addAll(right);
return left;
};
}
@Override
public BinaryOperator<List<O>> combiner() {
return (left, right) -> {
left.addAll(right);
return left;
};
}
@Override
public Function<List<O>, O[]> finisher() {
return list -> {
@SuppressWarnings("unchecked")
final O[] array = (O[]) Array.newInstance(elementType, list.size());
return list.toArray(array);
};
}
@Override
public Function<List<O>, O[]> finisher() {
return list -> {
@SuppressWarnings("unchecked")
final O[] array = (O[]) Array.newInstance(elementType, list.size());
return list.toArray(array);
};
}
@Override
public Supplier<List<O>> supplier() {
return ArrayList::new;
@Override
public Supplier<List<O>> supplier() {
return ArrayList::new;
}
}
}
/**
* A reduced, and simplified version of a {@link Stream} with
* failable method signatures.
* @param <O> The streams element type.
*/
public static class FailableStream<O extends Object> {
* A reduced, and simplified version of a {@link Stream} with failable method signatures.
*
* @param <O> The streams element type.
*/
public static class FailableStream<O extends Object> {
private Stream<O> stream;
private boolean terminated;
private Stream<O> stream;
private boolean terminated;
/**
* Constructs a new instance with the given {@code stream}.
* @param stream The stream.
*/
public FailableStream(final Stream<O> stream) {
this.stream = stream;
}
/**
* Constructs a new instance with the given {@code stream}.
*
* @param stream The stream.
*/
public FailableStream(final Stream<O> 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.
*
* \@apiNote
* 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<O, ?> predicate) {
assertNotTerminated();
return stream().allMatch(Failable.asPredicate(predicate));
}
/**
* 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.
*
* \@apiNote 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<O, ?> 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.
*
* \@apiNote
* 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<O, ?> predicate) {
assertNotTerminated();
return stream().anyMatch(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.
*
* \@apiNote 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<O, ?> predicate) {
assertNotTerminated();
return stream().anyMatch(Failable.asPredicate(predicate));
}
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
* {@code Collector}. A {@code 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 {@code 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>This is a terminal operation.
*
* <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 {@code ArrayList}), no
* additional synchronization is needed for a parallel reduction.
*
* \@apiNote
* 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:
* <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 {@code Collector}s together:
* <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 {@code Collector}
* @param collector the {@code 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 O, 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 {@code 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>This is a terminal operation.
*
* \@apiNote 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 {@code ArrayList}:
* <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:
* <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 pupplier 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> pupplier, final BiConsumer<R, ? super O> accumulator, final BiConsumer<R, R> combiner) {
makeTerminated();
return stream().collect(pupplier, accumulator, combiner);
}
/**
* Returns a FailableStream consisting of the elements of this stream that match
* the given FailablePredicate.
*
* <p>This is an intermediate operation.
*
* @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<O> filter(final FailablePredicate<O, ?> 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>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.
*
* @param action a non-interfering action to perform on the elements
*/
public void forEach(final FailableConsumer<O, ?> action) {
makeTerminated();
stream().forEach(Failable.asConsumer(action));
}
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.
*
* @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<O, 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>This is a terminal operation.
*
* \@apiNote 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.
*
* @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 O reduce(final O identity, final BinaryOperator<O> 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<O> stream() {
return stream;
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 {@code Collector}. A
* {@code 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 {@code 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>
* This is a terminal operation.
*
* <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 {@code ArrayList}), no additional synchronization is needed for a parallel
* reduction.
*
* \@apiNote The following will accumulate strings into an ArrayList:
*
* <pre>
* {
* &#64;code
* List<String> asList = stringStream.collect(Collectors.toList());
* }
* </pre>
*
* <p>
* The following will classify {@code Person} objects by city:
*
* <pre>
* {
* &#64;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 {@code Collector}s
* together:
*
* <pre>
* {
* &#64;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 {@code Collector}
* @param collector the {@code 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 O, 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 {@code 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>
* This is a terminal operation.
*
* \@apiNote 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
* {@code ArrayList}:
*
* <pre>
* {
* &#64;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:
*
* <pre>
* {
* &#64;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 pupplier 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> pupplier, final BiConsumer<R, ? super O> accumulator,
final BiConsumer<R, R> combiner) {
makeTerminated();
return stream().collect(pupplier, accumulator, combiner);
}
/**
* Returns a FailableStream consisting of the elements of this stream that match the given FailablePredicate.
*
* <p>
* This is an intermediate operation.
*
* @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<O> filter(final FailablePredicate<O, ?> 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>
* 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.
*
* @param action a non-interfering action to perform on the elements
*/
public void forEach(final FailableConsumer<O, ?> action) {
makeTerminated();
stream().forEach(Failable.asConsumer(action));
}
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.
*
* @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<O, 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>
* This is a terminal operation.
*
* \@apiNote Sum, min, max, average, and string concatenation are all special cases of reduction. Summing a
* stream of numbers can be expressed as:
*
* <pre>
* {
* &#64;code
* Integer sum = integers.reduce(0, (a, b) -> a + b);
* }
* </pre>
*
* or:
*
* <pre>
* {
* &#64;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.
*
* @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 O reduce(final O identity, final BinaryOperator<O> 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<O> 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:
* 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>
* final List&lt;O&gt; list;
* final Method m;
* final Function&lt;O,String&gt; mapper = (o) -&gt; {
* try {
* return (String) m.invoke(o);
* } catch (Throwable t) {
* throw Failable.rethrow(t);
* }
* };
* final List&lt;String&gt; strList = list.stream()
* .map(mapper).collect(Collectors.toList());
* </pre>
* as follows:
* <pre>
* final List&lt;O&gt; list;
* final Method m;
* final List&lt;String&gt; strList = Failable.stream(list.stream())
* .map((o) -&gt; (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.
* final List&lt;O&gt; list;
* final Method m;
* final Function&lt;O, String&gt; mapper = (o) -&gt; {
* try {
* return (String) m.invoke(o);
* } catch (Throwable t) {
* throw Failable.rethrow(t);
* }
* };
* final List&lt;String&gt; strList = list.stream().map(mapper).collect(Collectors.toList());
* </pre>
*
* as follows:
*
* <pre>
* final List&lt;O&gt; list;
* final Method m;
* final List&lt;String&gt; strList = Failable.stream(list.stream()).map((o) -&gt; (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 <O> The streams element type.
* @param stream The stream, which is being converted.
* @return The {@link FailableStream}, which has been created by
* converting the stream.
* @return The {@link FailableStream}, which has been created by converting the stream.
*/
public static <O> FailableStream<O> stream(final Collection<O> stream) {
return stream(stream.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:
* 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>
* final List&lt;O&gt; list;
* final Method m;
* final Function&lt;O,String&gt; mapper = (o) -&gt; {
* try {
* return (String) m.invoke(o);
* } catch (Throwable t) {
* throw Failable.rethrow(t);
* }
* };
* final List&lt;String&gt; strList = list.stream()
* .map(mapper).collect(Collectors.toList());
* </pre>
* as follows:
* <pre>
* final List&lt;O&gt; list;
* final Method m;
* final List&lt;String&gt; strList = Failable.stream(list.stream())
* .map((o) -&gt; (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.
* final List&lt;O&gt; list;
* final Method m;
* final Function&lt;O, String&gt; mapper = (o) -&gt; {
* try {
* return (String) m.invoke(o);
* } catch (Throwable t) {
* throw Failable.rethrow(t);
* }
* };
* final List&lt;String&gt; strList = list.stream().map(mapper).collect(Collectors.toList());
* </pre>
*
* as follows:
*
* <pre>
* final List&lt;O&gt; list;
* final Method m;
* final List&lt;String&gt; strList = Failable.stream(list.stream()).map((o) -&gt; (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 <O> The streams element type.
* @param stream The stream, which is being converted.
* @return The {@link FailableStream}, which has been created by
* converting the stream.
* @return The {@link FailableStream}, which has been created by converting the stream.
*/
public static <O> FailableStream<O> stream(final Stream<O> stream) {
return new FailableStream<>(stream);
}
/**
* Returns a {@code Collector} that accumulates the input elements into a
* new array.
* Returns a {@code Collector} that accumulates the input elements into a new array.
*
* @param pElementType Type of an element in the array.
* @param <O> the type of the input elements
* @return a {@code Collector} which collects all the input elements into an
* array, in encounter order
* @return a {@code Collector} which collects all the input elements into an array, in encounter order
*/
public static <O extends Object> Collector<O, ?, O[]> toArray(final Class<O> pElementType) {
return new ArrayCollector<>(pElementType);