Pair.java
/*
* *************************************************************************************************************************************************************
*
* TheseFoolishThings: Miscellaneous utilities
* http://tidalwave.it/projects/thesefoolishthings
*
* Copyright (C) 2009 - 2025 by Tidalwave s.a.s. (http://tidalwave.it)
*
* *************************************************************************************************************************************************************
*
* 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.
*
* *************************************************************************************************************************************************************
*
* git clone https://bitbucket.org/tidalwave/thesefoolishthings-src
* git clone https://github.com/tidalwave-it/thesefoolishthings-src
*
* *************************************************************************************************************************************************************
*/
package it.tidalwave.util;
// import javax.annotation.Nonnegative;
// import javax.annotation.concurrent.Immutable;
// import javax.annotation.concurrent.NotThreadSafe;
import jakarta.annotation.Nonnull;
import java.util.Map;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.IntFunction;
import java.util.function.IntUnaryOperator;
import java.util.stream.Collector;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;
import lombok.EqualsAndHashCode;
import lombok.Getter;
import lombok.RequiredArgsConstructor;
import lombok.ToString;
/***************************************************************************************************************************************************************
*
* A value object that contains a pair of values. Some factory methods allow creating pairs out of existing collections or arrays associating an index.
*
* @param <A> the type of the former element
* @param <B> the type of the latter element
* @author Fabrizio Giudici
* @since 3.2-ALPHA-6
* @it.tidalwave.javadoc.draft
*
**************************************************************************************************************************************************************/
@Getter /* @Immutable */ @RequiredArgsConstructor(staticName = "of") @ToString @EqualsAndHashCode
public class Pair<A, B>
{
/** A base 0 index rebaser. */
public static final IntUnaryOperator BASE_0 = i -> i;
/** A base 1 index rebaser. */
public static final IntUnaryOperator BASE_1 = i -> i + 1;
@Nonnull
public final A a;
@Nonnull
public final B b;
/***********************************************************************************************************************************************************
* {@return a new {@link Stream} of {@code Pair}s composed of a given fixed value and another element taken from another {@link Stream}}.
* @param <T> the type of the value
* @param <U> the type of the {@code Stream}
* @param value the value
* @param stream the {@code Stream}
* @since 3.2-ALPHA-12
**********************************************************************************************************************************************************/
@Nonnull
public static <T, U> Stream<Pair<T, U>> pairStream (@Nonnull final T value, @Nonnull final Stream<? extends U> stream)
{
return stream.map(object -> Pair.of(value, object));
}
/***********************************************************************************************************************************************************
* {@return a new {@link Stream} of {@code Pair}s composed of a given fixed value and an integer in the given range}.
* @param <T> the type of the value
* @param value the value
* @param from the first value of the integer {@code Stream} (included)
* @param to the last value of the integer {@code Stream} (excluded)
* @return the {@code Stream} of {@code Pair}s
**********************************************************************************************************************************************************/
@Nonnull
public static <T> Stream<Pair<T, Integer>> pairRange (@Nonnull final T value, /* @Nonnegative */ final int from, /* @Nonnegative */ final int to)
{
return pairStream(value, IntStream.range(from, to).boxed());
}
/***********************************************************************************************************************************************************
* {@return a new {@link Stream} of {@code Pair}s composed of a given fixed value and an integer in the given range}.
* @param <T> the type of the value
* @param value the value
* @param from the first value of the integer {@code Stream} (included)
* @param to the last value of the integer {@code Stream} (included)
* @since 3.2-ALPHA-12
**********************************************************************************************************************************************************/
@Nonnull
public static <T> Stream<Pair<T, Integer>> pairRangeClosed (@Nonnull final T value, /* @Nonnegative */ final int from, /* @Nonnegative */ final int to)
{
return pairStream(value, IntStream.rangeClosed(from, to).boxed());
}
/***********************************************************************************************************************************************************
* {@return a new {@link Stream} out of the elements in a given array made of {@link Pair}s {@code (index, value)}}.
* @param <T> the type of the elements
* @param array the array
* @see #isEven(Pair)
* @see #isOdd(Pair)
**********************************************************************************************************************************************************/
@Nonnull
public static <T> Stream<Pair<Integer, T>> indexedPairStream (@Nonnull final T[] array)
{
return indexedPairStream(array, BASE_0);
}
/***********************************************************************************************************************************************************
* {@return a new {@link Stream} out of the elements in the array, made of {@link Pair}s {@code (index, value)}}. The index can be rebased.
* @param <T> the type of the elements
* @param array the array
* @param rebaser the rebaser of the index (BASE_0, BASE_1 or a similar function)
* @see #isEven(Pair)
* @see #isOdd(Pair)
**********************************************************************************************************************************************************/
@Nonnull
public static <T> Stream<Pair<Integer, T>> indexedPairStream (@Nonnull final T[] array, @Nonnull final IntUnaryOperator rebaser)
{
return indexedPairStream(array, rebaser, i -> i);
}
/***********************************************************************************************************************************************************
* {@return a new {@link Stream} out of the elements in a given array made of {@link Pair}s {@code (index, value)}}. The index is transformed with the given
* function.
* @param <I> the type of the transformed index
* @param <T> the type of the elements
* @param array the array
* @param indexTransformer the transformer of the index
**********************************************************************************************************************************************************/
@Nonnull
public static <I, T> Stream<Pair<I, T>> indexedPairStream (@Nonnull final T[] array, @Nonnull final IntFunction<? extends I> indexTransformer)
{
return indexedPairStream(array, BASE_0, indexTransformer);
}
/***********************************************************************************************************************************************************
* {@return a new {@link Stream} out of the elements in the array, made of {@link Pair}s {@code (index, value)}}. The index can be rebased and transformed
* with specific functions.
* @param <T> the type of the elements
* @param <I> the type of the transformed index
* @param array the array
* @param rebaser the rebaser of the index (BASE_0, BASE_1 or a similar function)
* @param indexTransformer the transformer of the index
**********************************************************************************************************************************************************/
@Nonnull
public static <T, I> Stream<Pair<I, T>> indexedPairStream (@Nonnull final T[] array,
@Nonnull final IntUnaryOperator rebaser,
@Nonnull final IntFunction<? extends I> indexTransformer)
{
return IntStream.range(0, array.length).mapToObj(i -> of(indexTransformer.apply(rebaser.applyAsInt(i)), array[i]));
}
/***********************************************************************************************************************************************************
* {@return a new {@link Stream} out of the elements in a given {@link Iterable} made of {@link Pair}s {@code (index, value)}}.
* @param <T> the type of the elements
* @param iterable the iterable
* @see #isEven(Pair)
* @see #isOdd(Pair)
**********************************************************************************************************************************************************/
@Nonnull
public static <T> Stream<Pair<Integer, T>> indexedPairStream (@Nonnull final Iterable<? extends T> iterable)
{
return indexedPairStream(iterable, BASE_0);
}
/***********************************************************************************************************************************************************
* {@return a new {@link Stream} out of the elements in a given {@link Iterable} made of {@link Pair}s {@code (index, value)}}. The index can be rebased.
* @param <T> the type of the elements
* @param iterable the iterable
* @param rebaser the rebaser of the index (BASE_0, BASE_1 or a similar function)
* @see #isEven(Pair)
* @see #isOdd(Pair)
**********************************************************************************************************************************************************/
@Nonnull
public static <T> Stream<Pair<Integer, T>> indexedPairStream (@Nonnull final Iterable<? extends T> iterable, @Nonnull final IntUnaryOperator rebaser)
{
return indexedPairStream(iterable, rebaser, i -> i);
}
/***********************************************************************************************************************************************************
* {@return a new {@link Stream} out of the elements in a given {@link Iterable} made of {@link Pair}s {@code (index, value)}}. The index is transformed
* with the given function.
* @param <I> the type of the transformed index
* @param <T> the type of the elements
* @param iterable the iterable
* @param indexTransformer the transformer of the index
**********************************************************************************************************************************************************/
@Nonnull
public static <I, T> Stream<Pair<I, T>> indexedPairStream (@Nonnull final Iterable<? extends T> iterable,
@Nonnull final IntFunction<? extends I> indexTransformer)
{
return indexedPairStream(iterable, BASE_0, indexTransformer);
}
/***********************************************************************************************************************************************************
* {@return a new {@link Stream} out of the elements returned by an iterable, made of {@link Pair}s {@code (index, value)}}. The index is rebased and
* transformed with specific functions.
* @param <T> the type of the elements
* @param <I> the type of the transformed index
* @param iterable the iterable
* @param rebaser the rebaser of the index (BASE_0, BASE_1 or a similar function)
* @param indexTransformer the transformer of the index
**********************************************************************************************************************************************************/
@Nonnull
public static <I, T> Stream<Pair<I, T>> indexedPairStream (@Nonnull final Iterable<? extends T> iterable,
@Nonnull final IntUnaryOperator rebaser,
@Nonnull final IntFunction<? extends I> indexTransformer)
{
return new Factory<I, T>().stream(iterable, rebaser, indexTransformer);
}
/***********************************************************************************************************************************************************
* {@return a new {@link Stream} out of the elements in a given {@link Stream} made of {@link Pair}s {@code (index, value)}}.
* @param <T> the type of the elements
* @param stream the stream
* @since 3.2-ALPHA-12
**********************************************************************************************************************************************************/
@Nonnull @SuppressWarnings("unchecked")
public static <T> Stream<Pair<Integer, T>> indexedPairStream (@Nonnull final Stream<? extends T> stream)
{
return indexedPairStream(((Stream<T>)stream)::iterator);
}
/***********************************************************************************************************************************************************
* {@return a new {@link Stream} out of the elements in a given {@link Stream} made of {@link Pair}s {@code (index, value)}}. The index can be rebased.
* @param <T> the type of the elements
* @param stream the stream
* @param rebaser the rebaser of the index ({@link #BASE_0}, {@link #BASE_1} or a similar function)
* @since 3.2-ALPHA-12
**********************************************************************************************************************************************************/
@Nonnull @SuppressWarnings("unchecked")
public static <T> Stream<Pair<Integer, T>> indexedPairStream (@Nonnull final Stream<? extends T> stream, @Nonnull final IntUnaryOperator rebaser)
{
return indexedPairStream(((Stream<T>)stream)::iterator, rebaser);
}
/***********************************************************************************************************************************************************
* {@return a new {@link Stream} out of the elements in a given {@link Stream} made of {@link Pair}s {@code (index, value)}}. The index is transformed with
* the given function.
* @param <I> the type of the transformed index
* @param <T> the type of the elements
* @param stream the stream
* @param indexTransformer the transformer of the index
* @since 3.2-ALPHA-12
**********************************************************************************************************************************************************/
@SuppressWarnings("unchecked")
@Nonnull
public static <I, T> Stream<Pair<I, T>> indexedPairStream (@Nonnull final Stream<? extends T> stream,
@Nonnull final IntFunction<? extends I> indexTransformer)
{
return indexedPairStream(((Stream<T>)stream)::iterator, indexTransformer);
}
/***********************************************************************************************************************************************************
* {@return a new {@link Stream} out of the elements returned by a Stream, made of {@link Pair}s {@code (index, value)}}. The index is rebased and
* transformed with specific functions.
* @param <T> the type of the elements
* @param <I> the type of the transformed index
* @param stream the stream
* @param rebaser the rebaser of the index ({@link #BASE_0}, {@link #BASE_1} or a similar function)
* @param indexTransformer the transformer of the index
* @since 3.2-ALPHA-12
**********************************************************************************************************************************************************/
@SuppressWarnings("unchecked")
@Nonnull
public static <I, T> Stream<Pair<I, T>> indexedPairStream (@Nonnull final Stream<? extends T> stream,
@Nonnull final IntUnaryOperator rebaser,
@Nonnull final IntFunction<? extends I> indexTransformer)
{
return indexedPairStream(((Stream<T>)stream)::iterator, rebaser, indexTransformer);
}
/***********************************************************************************************************************************************************
* {@return a new {@link Stream} out of the elements returned by a supplier, made of {@link Pair}s {@code (index, value)}}.
* @param <T> the type of the elements
* @param from the first index (included)
* @param to the last index (excluded)
* @param valueSupplier the supplier of values
**********************************************************************************************************************************************************/
@Nonnull
public static <T> Stream<Pair<Integer, T>> indexedPairStream (/* @Nonnegative */ final int from,
/* @Nonnegative */ final int to,
@Nonnull final IntFunction<? extends T> valueSupplier)
{
return indexedPairStream(from, to, valueSupplier, BASE_0, i -> i);
}
/***********************************************************************************************************************************************************
* {@return a new {@link Stream} out of the elements returned by a supplier, made of {@link Pair}s {@code (index, value)}}.
* @param <T> the type of the elements
* @param from the first index (included)
* @param to the last index (excluded)
* @param valueSupplier the supplier of values
* @param rebaser the rebaser of the index ({@link #BASE_0}, {@link #BASE_1} or a similar function)
**********************************************************************************************************************************************************/
@Nonnull
public static <T> Stream<Pair<Integer, T>> indexedPairStream (/* @Nonnegative */ final int from,
/* @Nonnegative */ final int to,
@Nonnull final IntFunction<? extends T> valueSupplier,
@Nonnull final IntUnaryOperator rebaser)
{
return indexedPairStream(from, to, valueSupplier, rebaser, i -> i);
}
/***********************************************************************************************************************************************************
* {@return a new {@link Stream} out of the elements returned by a supplier, made of {@link Pair}s {@code (index, value)}}. The index can be rebased and
* transformed with specific functions.
* @param <I> the type of the transformed index
* @param <T> the type of the elements
* @param from the first index (included)
* @param to the last index (excluded)
* @param valueSupplier the supplier of values
* @param rebaser the rebaser of the index ({@link #BASE_0}, {@link #BASE_1} or a similar function)
* @param indexTransformer the transformer of the index
**********************************************************************************************************************************************************/
@Nonnull
public static <T, I> Stream<Pair<I, T>> indexedPairStream (/* @Nonnegative */ final int from,
/* @Nonnegative */ final int to,
@Nonnull final IntFunction<? extends T> valueSupplier,
@Nonnull final IntUnaryOperator rebaser,
@Nonnull final IntFunction<? extends I> indexTransformer)
{
return IntStream.range(from, to).mapToObj(i -> Pair.of(indexTransformer.apply(rebaser.applyAsInt(i)), valueSupplier.apply(i)));
}
/***********************************************************************************************************************************************************
* {@return a new {@link Collector} that produces a {@link Map} whose key is field {@code a} and value field {@code b}}.
* Use with {@link Stream#collect(Collector)}.
* @param <A> the type of the former element of the pair
* @param <B> the type of the latter element of the pair
* @return the {@code Collector}
**********************************************************************************************************************************************************/
@Nonnull
public static <A, B> Collector<Pair<A, B>, ?, Map<A, B>> pairsToMap()
{
return Collectors.toMap(p -> p.a, p -> p.b);
}
/***********************************************************************************************************************************************************
* {@return a new stream of {@link Pair}s created by “zipping” together two existing streams}.
* @param streamA the first {@link Stream}
* @param streamB the second {@link Stream}
* @param <A> the type of elements of the first {@link Stream}
* @param <B> the type of elements of the second {@link Stream}
* @since 3.2-ALPHA-17 (since 3.2-ALPHA-12 was in {@code StreamOperations}
**********************************************************************************************************************************************************/
@Nonnull
public static <A, B> Stream<Pair<A, B>> zip (@Nonnull final Stream<? extends A> streamA, @Nonnull final Stream<? extends B> streamB)
{
return StreamUtils.zip(streamA, streamB);
}
/***********************************************************************************************************************************************************
* {@return {@code true} if the given pair with an integer member has an even integer}.
* @param pair the pair
* @since 5.0-ALPHA-3
* @see #indexedPairStream(Object[])
**********************************************************************************************************************************************************/
public static boolean isEven (@Nonnull final Pair<Integer, ?> pair)
{
return pair.a % 2 == 0;
}
/***********************************************************************************************************************************************************
* {@return {@code true} if the given pair with an integer member has an odd integer}.
* @param pair the pair
* @since 5.0-ALPHA-3
* @see #indexedPairStream(Object[])
**********************************************************************************************************************************************************/
public static boolean isOdd (@Nonnull final Pair<Integer, ?> pair)
{
return pair.a % 2 != 0;
}
/***********************************************************************************************************************************************************
* A factory for indexed streams.
**********************************************************************************************************************************************************/
/* @NotThreadSafe */
static final class Factory<I, T>
{
private final AtomicInteger n = new AtomicInteger(0);
@Nonnull
public Stream<Pair<I, T>> stream (@Nonnull final Iterable<? extends T> iterable,
@Nonnull final IntUnaryOperator rebaser,
@Nonnull final IntFunction<? extends I> indexFunction)
{
return StreamSupport.stream(iterable.spliterator(), false)
.map(o -> Pair.of(indexFunction.apply(rebaser.applyAsInt(n.getAndIncrement())), o));
}
}
}