/**
*
* Copyright (c) 2006-2017, Speedment, Inc. All Rights Reserved.
*
* Licensed 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 com.speedment.common.singletonstream;
import static com.speedment.common.singletonstream.internal.SingletonUtil.STRICT;
import static com.speedment.common.singletonstream.internal.SingletonUtil.TRIPWIRE_ENABLED;
import static com.speedment.common.singletonstream.internal.SingletonUtil.trip;
import java.util.IntSummaryStatistics;
import java.util.NoSuchElementException;
import java.util.Objects;
import static java.util.Objects.requireNonNull;
import java.util.OptionalDouble;
import java.util.OptionalInt;
import java.util.PrimitiveIterator;
import java.util.Spliterator;
import java.util.function.BiConsumer;
import java.util.function.IntBinaryOperator;
import java.util.function.IntConsumer;
import java.util.function.IntFunction;
import java.util.function.IntPredicate;
import java.util.function.IntToDoubleFunction;
import java.util.function.IntToLongFunction;
import java.util.function.IntUnaryOperator;
import java.util.function.ObjIntConsumer;
import java.util.function.Supplier;
import java.util.stream.DoubleStream;
import java.util.stream.IntStream;
import java.util.stream.LongStream;
import java.util.stream.Stream;
/**
* An implementation of an IntStream that takes exactly one element as its
* source.
*
* This implementation supports optimized implementations of most terminal
* operations and a some number of intermediate operations. Un-optimized
* operations just returns a wrapped standard IntStream implementation.
*
* For performance reasons, the IntStream does not throw an
* IllegalStateOperation if methods are called after a terminal operation has
* been called on the Stream. This could be implemented using a boolean value
* set by each terminating op. All other ops could then assert this flag.
*
* @author Per Minborg
* @since 1.0.0
*/
public class SingletonIntStream implements IntStream {
private final int element;
private SingletonIntStream(int element) {
this.element = element;
}
public static IntStream of(int element) {
return new SingletonIntStream(element);
}
@Override
public IntStream filter(IntPredicate predicate) {
requireNonNull(predicate);
if (STRICT) {
return toStream().filter(predicate);
}
return predicate.test(element) ? this : empty();
}
@Override
public IntStream map(IntUnaryOperator mapper) {
requireNonNull(mapper);
if (STRICT) {
return toStream().map(mapper);
}
return of(mapper.applyAsInt(element));
}
@Override
public <U> Stream<U> mapToObj(IntFunction<? extends U> mapper) {
requireNonNull(mapper);
if (STRICT) {
return toStream().mapToObj(mapper);
}
return SingletonStream.of(mapper.apply(element));
}
@Override
public LongStream mapToLong(IntToLongFunction mapper) {
requireNonNull(mapper);
if (STRICT) {
return toStream().mapToLong(mapper);
}
return SingletonLongStream.of(mapper.applyAsLong(element));
}
@Override
public DoubleStream mapToDouble(IntToDoubleFunction mapper) {
requireNonNull(mapper);
if (STRICT) {
return toStream().mapToDouble(mapper);
}
return DoubleStream.of(mapper.applyAsDouble(element));
}
@Override
public IntStream flatMap(IntFunction<? extends IntStream> mapper) {
requireNonNull(mapper);
if (STRICT) {
return toStream().flatMap(mapper);
}
return mapper.apply(element);
}
@Override
public IntStream distinct() {
return this;
}
@Override
public IntStream sorted() {
return this;
}
@Override
public IntStream peek(IntConsumer action) {
requireNonNull(action);
return toStream().peek(action);
}
@Override
public IntStream limit(long maxSize) {
if (maxSize == 0) {
return empty();
}
if (maxSize > 0) {
return this;
}
throw new IllegalArgumentException(Long.toString(maxSize));
}
@Override
public IntStream skip(long n) {
if (n == 0) {
return this;
}
if (n > 0) {
return empty();
}
throw new IllegalArgumentException(Long.toString(n));
}
@Override
public void forEach(IntConsumer action) {
requireNonNull(action);
action.accept(element);
}
@Override
public void forEachOrdered(IntConsumer action) {
requireNonNull(action);
action.accept(element);
}
@Override
public int[] toArray() {
final int[] result = new int[1];
result[0] = element;
return result;
}
@Override
public int reduce(int identity, IntBinaryOperator op) {
requireNonNull(op);
return op.applyAsInt(identity, element);
}
@Override
public OptionalInt reduce(IntBinaryOperator op) {
// Just one element so the accumulator is never called.
return toOptional();
}
@Override
public <R> R collect(Supplier<R> supplier, ObjIntConsumer<R> accumulator, BiConsumer<R, R> combiner) {
requireNonNull(supplier);
requireNonNull(accumulator);
final R value = supplier.get();
accumulator.accept(value, element);
// the combiner is never used in a non-parallell stream
return value;
}
@Override
public int sum() {
return element;
}
@Override
public OptionalInt min() {
return toOptional();
}
@Override
public OptionalInt max() {
return toOptional();
}
@Override
public long count() {
return 1;
}
@Override
public OptionalDouble average() {
return OptionalDouble.of(element);
}
@Override
public IntSummaryStatistics summaryStatistics() {
final IntSummaryStatistics result = new IntSummaryStatistics();
result.accept(element);
return result;
}
@Override
public boolean anyMatch(IntPredicate predicate) {
requireNonNull(predicate);
return predicate.test(element);
}
@Override
public boolean allMatch(IntPredicate predicate) {
requireNonNull(predicate);
return predicate.test(element);
}
@Override
public boolean noneMatch(IntPredicate predicate) {
requireNonNull(predicate);
return !predicate.test(element);
}
@Override
public OptionalInt findFirst() {
return toOptional();
}
@Override
public OptionalInt findAny() {
return toOptional();
}
@Override
public LongStream asLongStream() {
return LongStream.of(element);
}
@Override
public DoubleStream asDoubleStream() {
return DoubleStream.of(element);
}
@Override
public Stream<Integer> boxed() {
return mapToObj(Integer::valueOf);
}
@Override
public IntStream sequential() {
return this;
}
@Override
public IntStream parallel() {
return toStream().parallel();
}
@Override
public PrimitiveIterator.OfInt iterator() {
return singletonIntIterator(element);
}
@Override
public Spliterator.OfInt spliterator() {
return singletonIntSpliterator(element);
}
@Override
public boolean isParallel() {
return false;
}
@Override
public IntStream unordered() {
return this; // Todo: may convey to singletonSpliterator()
}
@Override
public IntStream onClose(Runnable closeHandler) {
return toStream().onClose(closeHandler);
}
@Override
public void close() {
// do nothing. OnClose createa a real Stream
}
private IntStream toStream() {
return IntStream.of(element);
}
private OptionalInt toOptional() {
// if element is null, Optional will throw an NPE
// just as the standard Stream implementation does.
return OptionalInt.of(element);
}
private static IntStream empty() {
return IntStream.empty();
}
private static PrimitiveIterator.OfInt singletonIntIterator(final int e) {
return new PrimitiveIterator.OfInt() {
private boolean hasNext = true;
@Override
public boolean hasNext() {
return hasNext;
}
@Override
public int nextInt() {
if (hasNext) {
hasNext = false;
return e;
}
throw new NoSuchElementException();
}
@Override
public Integer next() {
if (TRIPWIRE_ENABLED) {
trip(getClass(), "{0} calling SingletonIntStream.singletonIterator.nextInt()");
}
return nextInt();
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
@Override
public void forEachRemaining(IntConsumer action) {
requireNonNull(action);
if (hasNext) {
action.accept(e);
hasNext = false;
}
}
};
}
private static Spliterator.OfInt singletonIntSpliterator(final int element) {
return new Spliterator.OfInt() {
long estimatedSize = 1;
@Override
public Spliterator.OfInt trySplit() {
return null;
}
@Override
public boolean tryAdvance(IntConsumer consumer) {
Objects.requireNonNull(consumer);
if (estimatedSize > 0) {
estimatedSize--;
consumer.accept(element);
return true;
}
return false;
}
@Override
public void forEachRemaining(IntConsumer consumer) {
tryAdvance(consumer);
}
@Override
public long estimateSize() {
return estimatedSize;
}
@Override
public int characteristics() {
return Spliterator.NONNULL | Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.IMMUTABLE
| Spliterator.DISTINCT | Spliterator.ORDERED;
}
};
}
// Java 9 Stream features
/**
* Returns, if this stream is ordered, a stream consisting of the longest
* prefix of elements taken from this stream that match the given predicate.
*
* @param predicate - a non-interfering, stateless predicate to apply to
* elements to determine the longest prefix of elements.
* @return the new stream
*/
public IntStream takeWhile(IntPredicate predicate) {
requireNonNull(predicate);
if (predicate.test(element)) {
return this;
} else {
return empty();
}
}
/**
* Returns, if this stream is ordered, a stream consisting of the remaining
* elements of this stream after dropping the longest prefix of elements
* that match the given predicate. Otherwise returns, if this stream is
* unordered, a stream consisting of the remaining elements of this stream
* after dropping a subset of elements that match the given predicate.
*
* @param predicate - a non-interfering, stateless predicate to apply to
* elements to determine the longest prefix of elements.
*
* @return new new stream
*/
public IntStream dropWhile(IntPredicate predicate) {
requireNonNull(predicate);
if (predicate.test(element)) {
return empty();
} else {
return this;
}
}
}