com.annimon.stream.DoubleStream Maven / Gradle / Ivy
package com.annimon.stream;
import java.io.Closeable;
import java.util.Comparator;
import com.annimon.stream.internal.Compose;
import com.annimon.stream.internal.Operators;
import com.annimon.stream.internal.Params;
import com.annimon.stream.iterator.PrimitiveExtIterator.OfDouble;
import com.annimon.stream.iterator.PrimitiveIterator;
import com.annimon.stream.operator.DoubleArray;
import com.annimon.stream.operator.DoubleConcat;
import com.annimon.stream.operator.DoubleDropWhile;
import com.annimon.stream.operator.DoubleFilter;
import com.annimon.stream.operator.DoubleFlatMap;
import com.annimon.stream.operator.DoubleGenerate;
import com.annimon.stream.operator.DoubleIterate;
import com.annimon.stream.operator.DoubleLimit;
import com.annimon.stream.operator.DoubleMap;
import com.annimon.stream.operator.DoubleMapToInt;
import com.annimon.stream.operator.DoubleMapToLong;
import com.annimon.stream.operator.DoubleMapToObj;
import com.annimon.stream.operator.DoublePeek;
import com.annimon.stream.operator.DoubleScan;
import com.annimon.stream.operator.DoubleScanIdentity;
import com.annimon.stream.operator.DoubleSkip;
import com.annimon.stream.operator.DoubleSorted;
import com.annimon.stream.operator.DoubleTakeUntil;
import com.annimon.stream.operator.DoubleTakeWhile;
import com.landawn.abacus.util.N;
import com.landawn.abacus.util.OptionalDouble;
import com.landawn.abacus.util.function.DoubleBinaryOperator;
import com.landawn.abacus.util.function.DoubleConsumer;
import com.landawn.abacus.util.function.DoubleFunction;
import com.landawn.abacus.util.function.DoublePredicate;
import com.landawn.abacus.util.function.DoubleSupplier;
import com.landawn.abacus.util.function.DoubleToIntFunction;
import com.landawn.abacus.util.function.DoubleToLongFunction;
import com.landawn.abacus.util.function.DoubleUnaryOperator;
import com.landawn.abacus.util.function.Function;
import com.landawn.abacus.util.function.ObjDoubleConsumer;
import com.landawn.abacus.util.function.Supplier;
import com.landawn.abacus.util.function.ToDoubleFunction;
/**
* A sequence of {@code double}-valued elements supporting aggregate operations.
*
* @since 1.1.4
* @see Stream
*/
public final class DoubleStream implements Closeable {
/**
* Single instance for empty stream. It is safe for multi-thread environment because it has no content.
*/
private static final DoubleStream EMPTY = new DoubleStream(new PrimitiveIterator.OfDouble() {
@Override
public boolean hasNext() {
return false;
}
@Override
public double nextDouble() {
return 0d;
}
});
/**
* Returns an empty stream.
*
* @return the empty stream
*/
public static DoubleStream empty() {
return EMPTY;
}
/**
* Creates a {@code DoubleStream} from the specified values.
*
* @param values the elements of the new stream
* @return the new stream
* @throws NullPointerException if {@code values} is null
*/
public static DoubleStream of(final double... values) {
if (values == null || values.length == 0) {
return DoubleStream.empty();
}
return new DoubleStream(new DoubleArray(values));
}
/**
* Creates a {@code DoubleStream} from {@code PrimitiveIterator.OfDouble}.
*
* @param iterator the iterator with elements to be passed to stream
* @return the new {@code DoubleStream}
* @throws NullPointerException if {@code iterator} is null
*/
public static DoubleStream of(PrimitiveIterator.OfDouble iterator) {
N.requireNonNull(iterator);
return new DoubleStream(iterator);
}
/**
* Creates a {@code DoubleStream} by elements that generated by {@code DoubleSupplier}.
*
* @param s the {@code DoubleSupplier} for generated elements
* @return a new infinite sequential {@code DoubleStream}
* @throws NullPointerException if {@code s} is null
*/
public static DoubleStream generate(final DoubleSupplier s) {
N.requireNonNull(s);
return new DoubleStream(new DoubleGenerate(s));
}
/**
* Creates a {@code DoubleStream} by iterative application {@code DoubleUnaryOperator} function
* to an initial element {@code seed}. Produces {@code DoubleStream} consisting of
* {@code seed}, {@code f(seed)}, {@code f(f(seed))}, etc.
*
* The first element (position {@code 0}) in the {@code DoubleStream} will be
* the provided {@code seed}. For {@code n > 0}, the element at position
* {@code n}, will be the result of applying the function {@code f} to the
* element at position {@code n - 1}.
*
*
Example:
*
* seed: 1
* f: (a) -> a + 5
* result: [1, 6, 11, 16, ...]
*
*
* @param seed the initial element
* @param f a function to be applied to the previous element to produce a new element
* @return a new sequential {@code DoubleStream}
* @throws NullPointerException if {@code f} is null
*/
public static DoubleStream iterate(final double seed, final DoubleUnaryOperator f) {
N.requireNonNull(f);
return new DoubleStream(new DoubleIterate(seed, f));
}
/**
* Creates an {@code DoubleStream} by iterative application {@code DoubleUnaryOperator} function
* to an initial element {@code seed}, conditioned on satisfying the supplied predicate.
*
* Example:
*
* seed: 0.0
* predicate: (a) -> a < 0.2
* f: (a) -> a + 0.05
* result: [0.0, 0.05, 0.1, 0.15]
*
*
* @param seed the initial value
* @param predicate a predicate to determine when the stream must terminate
* @param op operator to produce new element by previous one
* @return the new stream
* @throws NullPointerException if {@code op} is null
* @since 1.1.5
*/
public static DoubleStream iterate(final double seed, final DoublePredicate predicate, final DoubleUnaryOperator op) {
N.requireNonNull(predicate);
return iterate(seed, op).takeWhile(predicate);
}
/**
* Concatenates two streams.
*
* Example:
*
* stream a: [1, 2, 3, 4]
* stream b: [5, 6]
* result: [1, 2, 3, 4, 5, 6]
*
*
* @param a the first stream
* @param b the second stream
* @return the new concatenated stream
* @throws NullPointerException if {@code a} or {@code b} is null
*/
public static DoubleStream concat(final DoubleStream a, final DoubleStream b) {
N.requireNonNull(a);
N.requireNonNull(b);
@SuppressWarnings("resource")
DoubleStream result = new DoubleStream(new DoubleConcat(a.iterator, b.iterator));
return result.onClose(Compose.closeables(a, b));
}
public static DoubleStream concat(final double[] a, final double[] b) {
return new DoubleStream(new DoubleConcat(OfDouble.of(a), OfDouble.of(b)));
}
private final PrimitiveIterator.OfDouble iterator;
private final Params params;
private DoubleStream(PrimitiveIterator.OfDouble iterator) {
this(null, iterator);
}
DoubleStream(Params params, PrimitiveIterator.OfDouble iterator) {
this.params = params;
this.iterator = iterator;
}
/**
* Returns internal {@code DoubleStream} iterator.
*
* @return internal {@code DoubleStream} iterator.
*/
public PrimitiveIterator.OfDouble iterator() {
return iterator;
}
/**
* Returns a {@code Stream} consisting of the elements of this stream,
* each boxed to an {@code Double}.
*
* This is an lazy intermediate operation.
*
* @return a {@code Stream} consistent of the elements of this stream,
* each boxed to an {@code Double}
*/
public Stream boxed() {
return new Stream<>(params, iterator);
}
/**
* Returns {@code DoubleStream} with elements that satisfy the given predicate.
*
* This is an intermediate operation.
*
*
Example:
*
* predicate: (a) -> a > 2
* stream: [1, 2, 3, 4, -8, 0, 11]
* result: [3, 4, 11]
*
*
* @param predicate the predicate used to filter elements
* @return the new stream
*/
public DoubleStream filter(final DoublePredicate predicate) {
return new DoubleStream(params, new DoubleFilter(iterator, predicate));
}
/**
* Returns an {@code DoubleStream} consisting of the results of applying the given
* function to the elements of this stream.
*
* This is an intermediate operation.
*
*
Example:
*
* mapper: (a) -> a + 5
* stream: [1, 2, 3, 4]
* result: [6, 7, 8, 9]
*
*
* @param mapper the mapper function used to apply to each element
* @return the new stream
* @see Stream#map(com.landawn.abacus.util.function.Function)
*/
public DoubleStream map(final DoubleUnaryOperator mapper) {
return new DoubleStream(params, new DoubleMap(iterator, mapper));
}
/**
* Returns a {@code Stream} consisting of the results of applying the given
* function to the elements of this stream.
*
* This is an intermediate operation.
*
* @param the type result
* @param mapper the mapper function used to apply to each element
* @return the new {@code Stream}
*/
public Stream mapToObj(final DoubleFunction mapper) {
return new Stream<>(params, new DoubleMapToObj<>(iterator, mapper));
}
/**
* Returns an {@code IntStream} consisting of the results of applying the given
* function to the elements of this stream.
*
* This is an intermediate operation.
*
* @param mapper the mapper function used to apply to each element
* @return the new {@code IntStream}
*/
public IntStream mapToInt(final DoubleToIntFunction mapper) {
return new IntStream(params, new DoubleMapToInt(iterator, mapper));
}
/**
* Returns an {@code LongStream} consisting of the results of applying the given
* function to the elements of this stream.
*
*
This is an intermediate operation.
*
* @param mapper the mapper function used to apply to each element
* @return the new {@code LongStream}
*/
public LongStream mapToLong(final DoubleToLongFunction mapper) {
return new LongStream(params, new DoubleMapToLong(iterator, mapper));
}
/**
* Returns a stream consisting of the results of replacing each element of
* this stream with the contents of a mapped stream produced by applying
* the provided mapping function to each element.
*
*
This is an intermediate operation.
*
*
Example:
*
* mapper: (a) -> [a, a + 5]
* stream: [1, 2, 3, 4]
* result: [1, 6, 2, 7, 3, 8, 4, 9]
*
*
* @param mapper the mapper function used to apply to each element
* @return the new stream
* @see Stream#flatMap(com.landawn.abacus.util.function.Function)
*/
public DoubleStream flatMap(final DoubleFunction mapper) {
return new DoubleStream(params, new DoubleFlatMap(iterator, mapper));
}
/**
* Returns a stream consisting of the distinct elements of this stream.
*
* This is a stateful intermediate operation.
*
*
Example:
*
* stream: [1, 4, 2, 3, 3, 4, 1]
* result: [1, 4, 2, 3]
*
*
* @return the new stream
*/
public DoubleStream distinct() {
return boxed().distinct().mapToDouble(UNBOX_FUNCTION);
}
/**
* Returns a stream consisting of the elements of this stream in sorted order.
*
* This is a stateful intermediate operation.
*
*
Example:
*
* stream: [3, 4, 1, 2]
* result: [1, 2, 3, 4]
*
*
* @return the new stream
*/
public DoubleStream sorted() {
return new DoubleStream(params, new DoubleSorted(iterator));
}
/**
* Returns a stream consisting of the elements of this stream
* in sorted order as determinated by provided {@code Comparator}.
*
* This is a stateful intermediate operation.
*
*
Example:
*
* comparator: (a, b) -> -a.compareTo(b)
* stream: [1, 2, 3, 4]
* result: [4, 3, 2, 1]
*
*
* @param comparator the {@code Comparator} to compare elements
* @return the new {@code DoubleStream}
*/
public DoubleStream sorted(Comparator comparator) {
return boxed().sorted(comparator).mapToDouble(UNBOX_FUNCTION);
}
/**
* Performs provided action on each element.
*
* This is an intermediate operation.
*
* @param action the action to be performed on each element
* @return the new stream
*/
public DoubleStream peek(final DoubleConsumer action) {
return new DoubleStream(params, new DoublePeek(iterator, action));
}
/**
* Returns a {@code DoubleStream} produced by iterative application of a accumulation function
* to reduction value and next element of the current stream.
* Produces a {@code DoubleStream} consisting of {@code value1}, {@code acc(value1, value2)},
* {@code acc(acc(value1, value2), value3)}, etc.
*
*
This is an intermediate operation.
*
*
Example:
*
* accumulator: (a, b) -> a + b
* stream: [1, 2, 3, 4, 5]
* result: [1, 3, 6, 10, 15]
*
*
* @param accumulator the accumulation function
* @return the new stream
* @throws NullPointerException if {@code accumulator} is null
* @since 1.1.6
*/
public DoubleStream scan(final DoubleBinaryOperator accumulator) {
N.requireNonNull(accumulator);
return new DoubleStream(params, new DoubleScan(iterator, accumulator));
}
/**
* Returns a {@code DoubleStream} produced by iterative application of a accumulation function
* to an initial element {@code identity} and next element of the current stream.
* Produces a {@code DoubleStream} consisting of {@code identity}, {@code acc(identity, value1)},
* {@code acc(acc(identity, value1), value2)}, etc.
*
* This is an intermediate operation.
*
*
Example:
*
* identity: 0
* accumulator: (a, b) -> a + b
* stream: [1, 2, 3, 4, 5]
* result: [0, 1, 3, 6, 10, 15]
*
*
* @param identity the initial value
* @param accumulator the accumulation function
* @return the new stream
* @throws NullPointerException if {@code accumulator} is null
* @since 1.1.6
*/
public DoubleStream scan(final double identity, final DoubleBinaryOperator accumulator) {
N.requireNonNull(accumulator);
return new DoubleStream(params, new DoubleScanIdentity(iterator, identity, accumulator));
}
/**
* Takes elements while the predicate returns {@code true}.
*
* This is an intermediate operation.
*
*
Example:
*
* predicate: (a) -> a < 3
* stream: [1, 2, 3, 4, 1, 2, 3, 4]
* result: [1, 2]
*
*
* @param predicate the predicate used to take elements
* @return the new {@code DoubleStream}
*/
public DoubleStream takeWhile(final DoublePredicate predicate) {
return new DoubleStream(params, new DoubleTakeWhile(iterator, predicate));
}
/**
* Takes elements while the predicate returns {@code false}.
* Once predicate condition is satisfied by an element, the stream
* finishes with this element.
*
* This is an intermediate operation.
*
*
Example:
*
* stopPredicate: (a) -> a > 2
* stream: [1, 2, 3, 4, 1, 2, 3, 4]
* result: [1, 2, 3]
*
*
* @param stopPredicate the predicate used to take elements
* @return the new {@code DoubleStream}
* @since 1.1.6
*/
public DoubleStream takeUntil(final DoublePredicate stopPredicate) {
return new DoubleStream(params, new DoubleTakeUntil(iterator, stopPredicate));
}
/**
* Drops elements while the predicate is true and returns the rest.
*
* This is an intermediate operation.
*
*
Example:
*
* predicate: (a) -> a < 3
* stream: [1, 2, 3, 4, 1, 2, 3, 4]
* result: [3, 4, 1, 2, 3, 4]
*
*
* @param predicate the predicate used to drop elements
* @return the new {@code DoubleStream}
*/
public DoubleStream dropWhile(final DoublePredicate predicate) {
return new DoubleStream(params, new DoubleDropWhile(iterator, predicate));
}
/**
* Returns a stream consisting of the elements of this stream, truncated
* to be no longer than {@code maxSize} in length.
*
* This is a short-circuiting stateful intermediate operation.
*
*
Example:
*
* maxSize: 3
* stream: [1, 2, 3, 4, 5]
* result: [1, 2, 3]
*
* maxSize: 10
* stream: [1, 2]
* result: [1, 2]
*
*
* @param maxSize the number of elements the stream should be limited to
* @return the new stream
* @throws IllegalArgumentException if {@code maxSize} is negative
*/
public DoubleStream limit(final long maxSize) {
if (maxSize < 0)
throw new IllegalArgumentException("maxSize cannot be negative");
if (maxSize == 0)
return DoubleStream.empty();
return new DoubleStream(params, new DoubleLimit(iterator, maxSize));
}
/**
* Skips first {@code n} elements and returns {@code DoubleStream} with remaining elements.
* If this stream contains fewer than {@code n} elements, then an
* empty stream will be returned.
*
* This is a stateful intermediate operation.
*
*
Example:
*
* n: 3
* stream: [1, 2, 3, 4, 5]
* result: [4, 5]
*
* n: 10
* stream: [1, 2]
* result: []
*
*
* @param n the number of elements to skip
* @return the new stream
* @throws IllegalArgumentException if {@code n} is negative
*/
public DoubleStream skip(final long n) {
if (n < 0)
throw new IllegalArgumentException("n cannot be negative");
if (n == 0)
return this;
return new DoubleStream(params, new DoubleSkip(iterator, n));
}
/**
* Performs an action for each element of this stream.
*
* This is a terminal operation.
*
* @param action the action to be performed on each element
*/
public void forEach(DoubleConsumer action) {
while (iterator.hasNext()) {
action.accept(iterator.nextDouble());
}
}
/**
* Performs a reduction on the elements of this stream, using the provided
* identity value and an associative accumulation function, and returns the
* reduced value.
*
*
The {@code identity} value must be an identity for the accumulator
* function. This means that for all {@code x},
* {@code accumulator.apply(identity, x)} is equal to {@code x}.
* The {@code accumulator} function must be an associative function.
*
*
This is a terminal operation.
*
*
Example:
*
* identity: 0
* accumulator: (a, b) -> a + b
* stream: [1, 2, 3, 4, 5]
* result: 15
*
*
* @param identity the identity value for the accumulating function
* @param accumulator the accumulation function
* @return the result of the reduction
* @see #sum()
* @see #min()
* @see #max()
*/
public double reduce(double identity, DoubleBinaryOperator accumulator) {
double result = identity;
while (iterator.hasNext()) {
final double value = iterator.nextDouble();
result = accumulator.applyAsDouble(result, value);
}
return result;
}
/**
* Performs a reduction on the elements of this stream, using an
* associative accumulation function, and returns an {@code OptionalDouble}
* describing the reduced value, if any.
*
* The {@code accumulator} function must be an associative function.
*
*
This is a terminal operation.
*
* @param accumulator the accumulation function
* @return the result of the reduction
* @see #reduce(com.landawn.abacus.util.function.DoubleBinaryOperator)
*/
public OptionalDouble reduce(DoubleBinaryOperator accumulator) {
boolean foundAny = false;
double result = 0;
while (iterator.hasNext()) {
final double value = iterator.nextDouble();
if (!foundAny) {
foundAny = true;
result = value;
} else {
result = accumulator.applyAsDouble(result, value);
}
}
return foundAny ? OptionalDouble.of(result) : OptionalDouble.empty();
}
/**
* Returns an array containing the elements of this stream.
*
*
This is a terminal operation.
*
* @return an array containing the elements of this stream
*/
public double[] toArray() {
return Operators.toDoubleArray(iterator);
}
/**
* Collects elements to {@code supplier} provided container by applying the given accumulation function.
*
*
This is a terminal operation.
*
* @param the type of the result
* @param supplier the supplier function that provides container
* @param accumulator the accumulation function
* @return the result of collect elements
* @see Stream#collect(com.landawn.abacus.util.function.Supplier, com.landawn.abacus.util.function.BiConsumer)
*/
public R collect(Supplier supplier, ObjDoubleConsumer accumulator) {
final R result = supplier.get();
while (iterator.hasNext()) {
final double value = iterator.nextDouble();
accumulator.accept(result, value);
}
return result;
}
/**
* Returns the sum of elements in this stream.
*
* @return the sum of elements in this stream
*/
public double sum() {
double sum = 0;
while (iterator.hasNext()) {
sum += iterator.nextDouble();
}
return sum;
}
/**
* Returns an {@code OptionalDouble} describing the minimum element of this
* stream, or an empty optional if this stream is empty.
*
* This is a terminal operation.
*
* @return the minimum element
*/
public OptionalDouble min() {
return reduce(new DoubleBinaryOperator() {
@Override
public double applyAsDouble(double left, double right) {
return Math.min(left, right);
}
});
}
/**
* Returns an {@code OptionalDouble} describing the maximum element of this
* stream, or an empty optional if this stream is empty.
*
*
This is a terminal operation.
*
* @return the maximum element
*/
public OptionalDouble max() {
return reduce(new DoubleBinaryOperator() {
@Override
public double applyAsDouble(double left, double right) {
return Math.max(left, right);
}
});
}
/**
* Returns the count of elements in this stream.
*
*
This is a terminal operation.
*
* @return the count of elements in this stream
*/
public long count() {
long count = 0;
while (iterator.hasNext()) {
iterator.nextDouble();
count++;
}
return count;
}
/**
* Returns the average of elements in this stream.
*
*
This is a terminal operation.
*
* @return the average of elements in this stream
*/
public OptionalDouble average() {
long count = 0;
double sum = 0d;
while (iterator.hasNext()) {
sum += iterator.nextDouble();
count++;
}
if (count == 0)
return OptionalDouble.empty();
return OptionalDouble.of(sum / count);
}
/**
* Tests whether all elements match the given 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.
*
*
This is a short-circuiting terminal operation.
*
*
Example:
*
* predicate: (a) -> a == 5
* stream: [1, 2, 3, 4, 5]
* result: true
*
* predicate: (a) -> a == 5
* stream: [5, 5, 5]
* result: true
*
*
* @param predicate the predicate used to match elements
* @return {@code true} if any elements of the stream match the provided
* predicate, otherwise {@code false}
*/
public boolean anyMatch(DoublePredicate predicate) {
while (iterator.hasNext()) {
if (predicate.test(iterator.nextDouble()))
return true;
}
return false;
}
/**
* Tests whether all elements match the given 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.
*
* This is a short-circuiting terminal operation.
*
*
Example:
*
* predicate: (a) -> a == 5
* stream: [1, 2, 3, 4, 5]
* result: false
*
* predicate: (a) -> a == 5
* stream: [5, 5, 5]
* result: true
*
*
* @param predicate the predicate used to match elements
* @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(DoublePredicate predicate) {
while (iterator.hasNext()) {
if (!predicate.test(iterator.nextDouble()))
return false;
}
return true;
}
/**
* Tests whether no elements match the given 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.
*
* This is a short-circuiting terminal operation.
*
*
Example:
*
* predicate: (a) -> a == 5
* stream: [1, 2, 3, 4, 5]
* result: false
*
* predicate: (a) -> a == 5
* stream: [1, 2, 3]
* result: true
*
*
* @param predicate the predicate used to match elements
* @return {@code true} if either no elements of the stream match the
* provided predicate or the stream is empty, otherwise {@code false}
*/
public boolean noneMatch(DoublePredicate predicate) {
while (iterator.hasNext()) {
if (predicate.test(iterator.nextDouble()))
return false;
}
return true;
}
/**
* Returns the first element wrapped by {@code OptionalDouble} class.
* If stream is empty, returns {@code OptionalDouble.empty()}.
*
* This is a short-circuiting terminal operation.
*
* @return an {@code OptionalDouble} with first element
* or {@code OptionalDouble.empty()} if stream is empty
*/
public OptionalDouble findFirst() {
if (iterator.hasNext()) {
return OptionalDouble.of(iterator.nextDouble());
}
return OptionalDouble.empty();
}
/**
* Returns the last element wrapped by {@code OptionalDouble} class.
* If stream is empty, returns {@code OptionalDouble.empty()}.
*
*
This is a short-circuiting terminal operation.
*
* @return an {@code OptionalDouble} with the last element
* or {@code OptionalDouble.empty()} if the stream is empty
* @since 1.1.8
*/
public OptionalDouble findLast() {
return reduce(new DoubleBinaryOperator() {
@Override
public double applyAsDouble(double left, double right) {
return right;
}
});
}
/**
* Applies custom operator on stream.
*
* Transforming function can return {@code DoubleStream} for intermediate operations,
* or any value for terminal operation.
*
*
Operator examples:
*
* // Intermediate operator
* public class Zip implements Function<DoubleStream, DoubleStream> {
*
* private final DoubleStream secondStream;
* private final DoubleBinaryOperator combiner;
*
* public Zip(DoubleStream secondStream, DoubleBinaryOperator combiner) {
* this.secondStream = secondStream;
* this.combiner = combiner;
* }
*
* @Override
* public DoubleStream apply(DoubleStream firstStream) {
* final PrimitiveIterator.OfDouble it1 = firstStream.iterator();
* final PrimitiveIterator.OfDouble it2 = secondStream.iterator();
* return DoubleStream.of(new PrimitiveIterator.OfDouble() {
* @Override
* public boolean hasNext() {
* return it1.hasNext() && it2.hasNext();
* }
*
* @Override
* public double nextDouble() {
* return combiner.applyAsDouble(it1.nextDouble(), it2.nextDouble());
* }
* });
* }
* }
*
* // Intermediate operator based on existing stream operators
* public class SkipAndLimit implements UnaryOperator<DoubleStream> {
*
* private final int skip, limit;
*
* public SkipAndLimit(int skip, int limit) {
* this.skip = skip;
* this.limit = limit;
* }
*
* @Override
* public DoubleStream apply(DoubleStream stream) {
* return stream.skip(skip).limit(limit);
* }
* }
*
* // Terminal operator
* public class DoubleSummaryStatistics implements Function<DoubleStream, double[]> {
* @Override
* public double[] apply(DoubleStream stream) {
* long count = 0;
* double sum = 0;
* final PrimitiveIterator.OfDouble it = stream.iterator();
* while (it.hasNext()) {
* count++;
* sum += it.nextDouble();
* }
* double average = (count == 0) ? 0 : (sum / (double) count);
* return new double[] {count, sum, average};
* }
* }
*
*
* @param the type of the result
* @param function a transforming function
* @return a result of the transforming function
* @see Stream#chain(com.landawn.abacus.util.function.Function)
* @throws NullPointerException if {@code function} is null
*/
public R __(Function transfer) {
return transfer.apply(this);
}
public void println() {
boxed().println();
}
/**
* Adds close handler to the current stream.
*
* This is an intermediate operation.
*
* @param closeHandler an action to execute when the stream is closed
* @return the new stream with the close handler
* @since 1.1.8
*/
public DoubleStream onClose(final Runnable closeHandler) {
N.requireNonNull(closeHandler);
final Params newParams;
if (params == null) {
newParams = new Params();
newParams.closeHandler = closeHandler;
} else {
newParams = params;
final Runnable firstHandler = newParams.closeHandler;
newParams.closeHandler = Compose.runnables(firstHandler, closeHandler);
}
return new DoubleStream(newParams, iterator);
}
/**
* Causes close handler to be invoked if it exists.
* Since most of the stream providers are lists or arrays,
* it is not necessary to close the stream.
*
* @since 1.1.8
*/
@Override
public void close() {
if (params != null && params.closeHandler != null) {
params.closeHandler.run();
params.closeHandler = null;
}
}
private static final ToDoubleFunction UNBOX_FUNCTION = new ToDoubleFunction() {
@Override
public double applyAsDouble(Double t) {
return t;
}
};
}