/*
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* CDDL HEADER START
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*
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* The contents of this file are subject to the terms of the
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* Common Development and Distribution License, Version 1.0 only
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* (the "License"). You may not use this file except in compliance
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* with the License.
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*
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* You can obtain a copy of the license at legal-notices/CDDLv1_0.txt
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* or http://forgerock.org/license/CDDLv1.0.html.
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* See the License for the specific language governing permissions
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* and limitations under the License.
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*
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* When distributing Covered Code, include this CDDL HEADER in each
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* file and include the License file at legal-notices/CDDLv1_0.txt.
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* If applicable, add the following below this CDDL HEADER, with the
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* fields enclosed by brackets "[]" replaced with your own identifying
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* information:
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* Portions Copyright [yyyy] [name of copyright owner]
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*
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* CDDL HEADER END
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*
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*
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* Copyright 2009-2010 Sun Microsystems, Inc.
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* Portions copyright 2013 ForgeRock AS.
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*/
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package com.forgerock.opendj.util;
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import java.util.Collection;
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import java.util.Iterator;
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import org.forgerock.opendj.ldap.Function;
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/**
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* Utility methods for manipulating {@link Iterable}s.
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*/
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public final class Iterables {
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private static abstract class AbstractIterable<M> implements Iterable<M> {
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@Override
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public String toString() {
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return Iterables.toString(this);
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}
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}
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private static final class ArrayIterable<M> extends AbstractIterable<M> {
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private final M[] a;
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// Constructed via factory methods.
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private ArrayIterable(final M[] a) {
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this.a = a;
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}
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@Override
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public Iterator<M> iterator() {
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return Iterators.arrayIterator(a);
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}
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}
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private static final class EmptyIterable<M> extends AbstractIterable<M> {
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@Override
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public Iterator<M> iterator() {
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return Iterators.emptyIterator();
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}
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}
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private static final class FilteredIterable<M, P> extends AbstractIterable<M> {
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private final Iterable<M> iterable;
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private final P parameter;
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private final Predicate<? super M, P> predicate;
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// Constructed via factory methods.
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private FilteredIterable(final Iterable<M> iterable,
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final Predicate<? super M, P> predicate, final P p) {
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this.iterable = iterable;
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this.predicate = predicate;
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this.parameter = p;
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}
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@Override
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public Iterator<M> iterator() {
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return Iterators.filteredIterator(iterable.iterator(), predicate, parameter);
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}
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}
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private static final class SingletonIterable<M> extends AbstractIterable<M> {
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private final M value;
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// Constructed via factory methods.
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private SingletonIterable(final M value) {
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this.value = value;
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}
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@Override
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public Iterator<M> iterator() {
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return Iterators.singletonIterator(value);
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}
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}
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private static final class TransformedIterable<M, N, P> extends AbstractIterable<N> {
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private final Function<? super M, ? extends N, P> function;
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private final Iterable<M> iterable;
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private final P parameter;
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// Constructed via factory methods.
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private TransformedIterable(final Iterable<M> iterable,
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final Function<? super M, ? extends N, P> function, final P p) {
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this.iterable = iterable;
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this.function = function;
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this.parameter = p;
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}
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@Override
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public Iterator<N> iterator() {
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return Iterators.transformedIterator(iterable.iterator(), function, parameter);
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}
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}
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private static final class UnmodifiableIterable<M> extends AbstractIterable<M> {
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private final Iterable<M> iterable;
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// Constructed via factory methods.
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private UnmodifiableIterable(final Iterable<M> iterable) {
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this.iterable = iterable;
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}
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@Override
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public Iterator<M> iterator() {
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return Iterators.unmodifiableIterator(iterable.iterator());
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}
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}
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private static final Iterable<Object> EMPTY_ITERABLE = new EmptyIterable<Object>();
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/**
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* Returns an iterable containing the elements of {@code a}. The returned
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* iterable's iterator does not support element removal via the
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* {@code remove()} method.
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*
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* @param <M>
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* The type of elements contained in {@code a}.
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* @param a
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* The array of elements.
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* @return An iterable containing the elements of {@code a}.
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*/
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public static <M> Iterable<M> arrayIterable(final M[] a) {
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return new ArrayIterable<M>(a);
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}
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/**
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* Returns an immutable empty iterable.
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*
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* @param <M>
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* The required type of the empty iterable.
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* @return An immutable empty iterable.
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*/
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@SuppressWarnings("unchecked")
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public static <M> Iterable<M> emptyIterable() {
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return (Iterable<M>) EMPTY_ITERABLE;
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}
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/**
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* Returns a filtered view of {@code iterable} containing only those
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* elements which match {@code predicate}. The returned iterable's iterator
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* supports element removal via the {@code remove()} method subject to any
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* constraints imposed by {@code iterable}.
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*
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* @param <M>
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* The type of elements contained in {@code iterable}.
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* @param <P>
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* The type of the additional parameter to the predicate's
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* {@code matches} method. Use {@link java.lang.Void} for
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* predicates that do not need an additional parameter.
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* @param iterable
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* The iterable to be filtered.
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* @param predicate
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* The predicate.
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* @param p
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* A predicate specified parameter.
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* @return A filtered view of {@code iterable} containing only those
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* elements which match {@code predicate}.
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*/
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public static <M, P> Iterable<M> filteredIterable(final Iterable<M> iterable,
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final Predicate<? super M, P> predicate, final P p) {
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return new FilteredIterable<M, P>(iterable, predicate, p);
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}
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/**
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* Returns a filtered view of {@code iterable} containing only those
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* elements which match {@code predicate}. The returned iterable's iterator
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* supports element removal via the {@code remove()} method subject to any
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* constraints imposed by {@code iterable}.
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*
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* @param <M>
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* The type of elements contained in {@code iterable}.
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* @param iterable
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* The iterable to be filtered.
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* @param predicate
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* The predicate.
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* @return A filtered view of {@code iterable} containing only those
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* elements which match {@code predicate}.
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*/
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public static <M> Iterable<M> filteredIterable(final Iterable<M> iterable,
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final Predicate<? super M, Void> predicate) {
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return new FilteredIterable<M, Void>(iterable, predicate, null);
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}
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/**
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* Returns {@code true} if the provided iterable does not contain any
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* elements.
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*
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* @param iterable
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* The iterable.
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* @return {@code true} if the provided iterable does not contain any
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* elements.
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*/
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public static boolean isEmpty(final Iterable<?> iterable) {
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if (iterable instanceof Collection) {
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// Fall-through if possible and potentially avoid allocation.
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return ((Collection<?>) iterable).isEmpty();
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} else {
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return !iterable.iterator().hasNext();
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}
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}
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/**
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* Returns an iterable containing the single element {@code value}. The
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* returned iterable's iterator does not support element removal via the
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* {@code remove()} method.
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*
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* @param <M>
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* The type of the single element {@code value}.
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* @param value
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* The single element.
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* @return An iterable containing the single element {@code value}.
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*/
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public static <M> Iterable<M> singletonIterable(final M value) {
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return new SingletonIterable<M>(value);
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}
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/**
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* Returns the number of elements contained in the provided iterable.
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*
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* @param iterable
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* The iterable.
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* @return The number of elements contained in the provided iterable.
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*/
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public static int size(final Iterable<?> iterable) {
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if (iterable instanceof Collection) {
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// Fall-through if possible and potentially benefit from constant time calculation.
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return ((Collection<?>) iterable).size();
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} else {
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final Iterator<?> i = iterable.iterator();
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int sz = 0;
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while (i.hasNext()) {
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i.next();
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sz++;
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}
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return sz;
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}
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}
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/**
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* Returns a string representation of the provided iterable composed of an
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* opening square bracket, followed by each element separated by commas, and
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* then a closing square bracket.
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*
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* @param iterable
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* The iterable whose string representation is to be returned.
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* @return A string representation of the provided iterable.
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* @see java.util.AbstractCollection#toString()
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*/
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public static String toString(final Iterable<?> iterable) {
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if (iterable instanceof Collection) {
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// Fall-through if possible.
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return ((Collection<?>) iterable).toString();
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} else {
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final StringBuilder builder = new StringBuilder();
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boolean firstValue = true;
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builder.append('[');
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for (final Object value : iterable) {
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if (!firstValue) {
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builder.append(", ");
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}
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builder.append(String.valueOf(value));
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firstValue = false;
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}
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builder.append(']');
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return builder.toString();
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}
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}
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/**
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* Returns a view of {@code iterable} whose values have been mapped to
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* elements of type {@code N} using {@code function}. The returned
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* iterable's iterator supports element removal via the {@code remove()}
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* method subject to any constraints imposed by {@code iterable}.
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*
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* @param <M>
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* The type of elements contained in {@code iterable}.
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* @param <N>
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* The type of elements contained in the returned iterable.
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* @param <P>
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* The type of the additional parameter to the function's
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* {@code apply} method. Use {@link java.lang.Void} for functions
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* that do not need an additional parameter.
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* @param iterable
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* The iterable to be transformed.
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* @param function
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* The function.
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* @param p
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* A predicate specified parameter.
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* @return A view of {@code iterable} whose values have been mapped to
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* elements of type {@code N} using {@code function}.
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*/
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public static <M, N, P> Iterable<N> transformedIterable(final Iterable<M> iterable,
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final Function<? super M, ? extends N, P> function, final P p) {
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return new TransformedIterable<M, N, P>(iterable, function, p);
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}
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/**
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* Returns a view of {@code iterable} whose values have been mapped to
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* elements of type {@code N} using {@code function}. The returned
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* iterable's iterator supports element removal via the {@code remove()}
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* method subject to any constraints imposed by {@code iterable}.
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*
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* @param <M>
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* The type of elements contained in {@code iterable}.
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* @param <N>
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* The type of elements contained in the returned iterable.
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* @param iterable
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* The iterable to be transformed.
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* @param function
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* The function.
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* @return A view of {@code iterable} whose values have been mapped to
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* elements of type {@code N} using {@code function}.
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*/
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public static <M, N> Iterable<N> transformedIterable(final Iterable<M> iterable,
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final Function<? super M, ? extends N, Void> function) {
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return new TransformedIterable<M, N, Void>(iterable, function, null);
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}
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/**
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* Returns a read-only view of {@code iterable} whose iterator does not
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* support element removal via the {@code remove()}. Attempts to use the
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* {@code remove()} method will result in a
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* {@code UnsupportedOperationException}.
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*
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* @param <M>
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* The type of elements contained in {@code iterable}.
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* @param iterable
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* The iterable to be made read-only.
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* @return A read-only view of {@code iterable} whose iterator does not
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* support element removal via the {@code remove()}.
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*/
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public static <M> Iterable<M> unmodifiableIterable(final Iterable<M> iterable) {
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return new UnmodifiableIterable<M>(iterable);
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}
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// Prevent instantiation
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private Iterables() {
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// Do nothing.
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}
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}
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