eaglercraft-1.8/sources/main/java/org/apache/commons/lang3/Streams.java

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2022-12-25 01:12:28 -08:00
/*
* 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;
import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Set;
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 org.apache.commons.lang3.Functions.FailableConsumer;
import org.apache.commons.lang3.Functions.FailableFunction;
import org.apache.commons.lang3.Functions.FailablePredicate;
/**
* Provides utility functions, and classes for working with the
* {@code 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>
* Consumer&lt;java.lang.reflect.Method&gt; consumer = m -&gt; {
* try {
* m.invoke(o, args);
* } catch (Throwable t) {
* throw Functions.rethrow(t);
* }
* };
* stream.forEach(consumer);
* </pre>
*
* Using a {@link FailableStream}, this can be rewritten as follows:
*
* <pre>
* Streams.failable(stream).forEach((m) -&gt; m.invoke(o, args));
* </pre>
*
* Obviously, the second version is much more concise and the spirit of Lambda
* expressions is met better than in the first version.
*
* @see Stream
* @see Functions
* @since 3.10
* @deprecated Use {@link org.apache.commons.lang3.stream.Streams}.
*/
@Deprecated
public class Streams {
/**
* A reduced, and simplified version of a {@link Stream} with failable method
* signatures.
*
* @param <O> The streams element type.
* @deprecated Use
* {@link org.apache.commons.lang3.stream.Streams.FailableStream}.
*/
@Deprecated
public static class FailableStream<O extends Object> {
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;
}
protected void assertNotTerminated() {
if (terminated) {
throw new IllegalStateException("This stream is already terminated.");
}
}
protected void makeTerminated() {
assertNotTerminated();
terminated = true;
}
/**
* 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(Functions.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(Functions.asConsumer(action));
}
/**
* 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.
*
* Note 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.
*
* 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 {@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);
}
/**
* 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.
*
* Note 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);
}
/**
* 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(Functions.asFunction(mapper)));
}
/**
* 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;
}
/**
* 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.
*
* 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<O, ?> predicate) {
assertNotTerminated();
return stream().allMatch(Functions.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.
*
* 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<O, ?> predicate) {
assertNotTerminated();
return stream().anyMatch(Functions.asPredicate(predicate));
}
}
/**
* 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 Functions.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 = Functions.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.
*/
public static <O> FailableStream<O> stream(final Stream<O> stream) {
return new FailableStream<>(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>
* 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 Functions.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 = Functions.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.
*/
public static <O> FailableStream<O> stream(final Collection<O> stream) {
return stream(stream.stream());
}
/**
* A Collector type for arrays.
*
* @param <O> The array type.
* @deprecated Use
* {@link org.apache.commons.lang3.stream.Streams.ArrayCollector}.
*/
@Deprecated
public static class ArrayCollector<O> implements Collector<O, List<O>, O[]> {
private static final Set<Characteristics> characteristics = Collections.emptySet();
private final Class<O> elementType;
/**
* Constructs a new instance for the given element type.
*
* @param elementType The element type.
*/
public ArrayCollector(final Class<O> elementType) {
this.elementType = elementType;
}
@Override
public Supplier<List<O>> supplier() {
return ArrayList::new;
}
@Override
public BiConsumer<List<O>, O> accumulator() {
return List::add;
}
@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 Set<Characteristics> characteristics() {
return characteristics;
}
}
/**
* 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
*/
public static <O extends Object> Collector<O, ?, O[]> toArray(final Class<O> pElementType) {
return new ArrayCollector<>(pElementType);
}
}