/* * The MIT License (MIT) * * Copyright (c) 2017-2020 Yegor Bugayenko * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included * in all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE * SOFTWARE. */ package org.cactoos.scalar; import java.util.Iterator; import java.util.NoSuchElementException; import org.cactoos.BiFunc; import org.cactoos.Scalar; import org.cactoos.iterable.Mapped; /** * Reduces iterable via BiFunc. * * <pre>{@code * new Reduced<>( * (first, last) -> first + last, * new IterableOf<>(() -> 1L, () -> 2L, () -> 3L, () -> 4L) * ).value() // returns 10L * }</pre> * * <p>Here is how you can use it to * find one of items according to the specified {@link BiFunc}:</p> * * <pre>{@code * final String apple = new Reduced<>( * (first, last) -> first, * new IterableOf<Scalar<String>>( * () -> "Apple", * () -> "Banana", * () -> "Orange" * ) * ).value(); * final String orange = new Reduced<>( * (first, last) -> last, * new IterableOf<Scalar<String>>( * () -> "Apple", * () -> "Banana", * () -> "Orange" * ) * ).value(); * }</pre> * * <p>There is no thread-safety guarantee. * * <p>This class implements {@link Scalar}, which throws a checked * {@link Exception}. This may not be convenient in many cases. To make * it more convenient and get rid of the checked exception you can * use the {@link Unchecked} decorator. Or you may use * {@link IoChecked} to wrap it in an IOException.</p> * * @param <T> Scalar type * @since 0.30 */ public final class Reduced<T> implements Scalar<T> { /** * Items. */ private final Iterable<Scalar<T>> items; /** * Folding function. */ private final BiFunc<T, T, T> function; /** * Ctor. * @param reduce Reducing function * @param scalars The scalars */ public Reduced( final BiFunc<T, T, T> reduce, final Iterable<Scalar<T>> scalars ) { this.items = scalars; this.function = reduce; } /** * Ctor. * @param reduce Reducing function * @param values Values to be wrapped as scalars */ @SafeVarargs public Reduced( final BiFunc<T, T, T> reduce, final T... values ) { this(reduce, new Mapped<>(Constant::new, values)); } @Override public T value() throws Exception { final Iterator<Scalar<T>> iter = this.items.iterator(); if (!iter.hasNext()) { throw new NoSuchElementException( "Can't find first element in an empty iterable" ); } T acc = iter.next().value(); while (iter.hasNext()) { final T next = iter.next().value(); acc = this.function.apply(acc, next); } return acc; } }