11d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert/* 21d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Copyright (C) 2010 The Guava Authors 31d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 41d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Licensed under the Apache License, Version 2.0 (the "License"); 51d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * you may not use this file except in compliance with the License. 61d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * You may obtain a copy of the License at 71d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 81d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * http://www.apache.org/licenses/LICENSE-2.0 91d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 101d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Unless required by applicable law or agreed to in writing, software 111d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * distributed under the License is distributed on an "AS IS" BASIS, 121d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 131d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * See the License for the specific language governing permissions and 141d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * limitations under the License. 151d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 161d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 171d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertpackage com.google.common.base; 181d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 191d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport static com.google.common.base.Preconditions.checkNotNull; 201d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 211d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport com.google.common.annotations.Beta; 221d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport com.google.common.annotations.GwtCompatible; 231d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 241d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport java.io.Serializable; 251d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 261d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertimport javax.annotation.Nullable; 271d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 281d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert/** 291d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * A strategy for determining whether two instances are considered equivalent. Examples of 301d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * equivalences are the {@link Equivalences#identity() identity equivalence} and {@link 311d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Equivalences#equals equals equivalence}. 321d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 331d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @author Bob Lee 341d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @author Ben Yu 351d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @author Gregory Kick 361d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 10.0 (<a href="http://code.google.com/p/guava-libraries/wiki/Compatibility" 371d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * >mostly source-compatible</a> since 4.0) 381d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 391d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert@Beta 401d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert@GwtCompatible 411d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringertpublic abstract class Equivalence<T> { 421d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 431d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Constructor for use by subclasses. 441d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 451d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert protected Equivalence() {} 461d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 471d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 481d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Returns {@code true} if the given objects are considered equivalent. 491d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 501d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <p>The {@code equivalent} method implements an equivalence relation on object references: 511d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 521d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <ul> 531d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <li>It is <i>reflexive</i>: for any reference {@code x}, including null, {@code 541d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * equivalent(x, x)} returns {@code true}. 551d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <li>It is <i>symmetric</i>: for any references {@code x} and {@code y}, {@code 561d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * equivalent(x, y) == equivalent(y, x)}. 571d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <li>It is <i>transitive</i>: for any references {@code x}, {@code y}, and {@code z}, if 581d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@code equivalent(x, y)} returns {@code true} and {@code equivalent(y, z)} returns {@code 591d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * true}, then {@code equivalent(x, z)} returns {@code true}. 601d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <li>It is <i>consistent</i>: for any references {@code x} and {@code y}, multiple invocations 611d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * of {@code equivalent(x, y)} consistently return {@code true} or consistently return {@code 621d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * false} (provided that neither {@code x} nor {@code y} is modified). 631d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * </ul> 641d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 651d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public final boolean equivalent(@Nullable T a, @Nullable T b) { 661d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert if (a == b) { 671d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return true; 681d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 691d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert if (a == null || b == null) { 701d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return false; 711d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 721d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return doEquivalent(a, b); 731d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 741d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 751d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 761d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Returns {@code true} if {@code a} and {@code b} are considered equivalent. 771d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 781d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <p>Called by {@link #equivalent}. {@code a} and {@code b} are not the same 791d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * object and are not nulls. 801d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 811d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 10.0 (previously, subclasses would override equivalent()) 821d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 831d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert protected abstract boolean doEquivalent(T a, T b); 841d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 851d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 861d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Returns a hash code for {@code t}. 871d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 881d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <p>The {@code hash} has the following properties: 891d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <ul> 901d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <li>It is <i>consistent</i>: for any reference {@code x}, multiple invocations of 911d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@code hash(x}} consistently return the same value provided {@code x} remains unchanged 921d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * according to the definition of the equivalence. The hash need not remain consistent from 931d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * one execution of an application to another execution of the same application. 941d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <li>It is <i>distributable accross equivalence</i>: for any references {@code x} and {@code y}, 951d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * if {@code equivalent(x, y)}, then {@code hash(x) == hash(y)}. It is <i>not</i> necessary 961d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * that the hash be distributable accorss <i>inequivalence</i>. If {@code equivalence(x, y)} 971d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * is false, {@code hash(x) == hash(y)} may still be true. 981d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <li>{@code hash(null)} is {@code 0}. 991d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * </ul> 1001d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 1011d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public final int hash(@Nullable T t) { 1021d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert if (t == null) { 1031d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return 0; 1041d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 1051d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return doHash(t); 1061d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 1071d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 1081d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 1091d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Returns a hash code for non-null object {@code t}. 1101d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 1111d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <p>Called by {@link #hash}. 1121d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 1131d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 10.0 (previously, subclasses would override hash()) 1141d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 1151d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert protected abstract int doHash(T t); 1161d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 1171d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 1181d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Returns a new equivalence relation for {@code F} which evaluates equivalence by first applying 1191d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@code function} to the argument, then evaluating using {@code this}. That is, for any pair of 1201d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * non-null objects {@code x} and {@code y}, {@code 1211d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * equivalence.onResultOf(function).equivalent(a, b)} is true if and only if {@code 1221d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * equivalence.equivalent(function.apply(a), function.apply(b))} is true. 1231d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 1241d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <p>For example: <pre> {@code 1251d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 1261d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Equivalence<Person> SAME_AGE = Equivalences.equals().onResultOf(GET_PERSON_AGE); 1271d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * }</pre> 1281d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 1291d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <p>{@code function} will never be invoked with a null value. 1301d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 1311d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <p>Note that {@code function} must be consistent according to {@code this} equivalence 1321d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * relation. That is, invoking {@link Function#apply} multiple times for a given value must return 1331d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * equivalent results. 1341d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * For example, {@code Equivalences.identity().onResultOf(Functions.toStringFunction())} is broken 1351d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * because it's not guaranteed that {@link Object#toString}) always returns the same string 1361d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * instance. 1371d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 1381d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 10.0 1391d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 1401d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public final <F> Equivalence<F> onResultOf(Function<F, ? extends T> function) { 1411d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return new FunctionalEquivalence<F, T>(function, this); 1421d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 1431d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 1441d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 1451d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Returns a wrapper of {@code reference} that implements 1461d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@link Wrapper#equals(Object) Object.equals()} such that 1471d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@code wrap(this, a).equals(wrap(this, b))} if and only if {@code this.equivalent(a, b)}. 1481d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 1491d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 10.0 1501d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 1511d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public final <S extends T> Wrapper<S> wrap(@Nullable S reference) { 1521d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return new Wrapper<S>(this, reference); 1531d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 1541d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 1551d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 1561d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Wraps an object so that {@link #equals(Object)} and {@link #hashCode()} delegate to an 1571d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@link Equivalence}. 1581d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 1591d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <p>For example, given an {@link Equivalence} for {@link String strings} named {@code equiv} 1601d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * that tests equivalence using their lengths: 1611d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 1621d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <pre> {@code 1631d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * equiv.wrap("a").equals(equiv.wrap("b")) // true 1641d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * equiv.wrap("a").equals(equiv.wrap("hello")) // false 1651d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * }</pre> 1661d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 1671d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <p>Note in particular that an equivalence wrapper is never equal to the object it wraps. 1681d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 1691d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <pre> {@code 1701d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * equiv.wrap(obj).equals(obj) // always false 1711d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * }</pre> 1721d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 1731d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 10.0 1741d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 1751d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Beta 1761d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public static final class Wrapper<T> implements Serializable { 1771d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert private final Equivalence<? super T> equivalence; 1781d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Nullable private final T reference; 1791d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 1801d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert private Wrapper(Equivalence<? super T> equivalence, @Nullable T reference) { 1811d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert this.equivalence = checkNotNull(equivalence); 1821d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert this.reference = reference; 1831d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 1841d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 1851d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** Returns the (possibly null) reference wrapped by this instance. */ 1861d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Nullable public T get() { 1871d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return reference; 1881d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 1891d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 1901d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 1911d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Returns {@code true} if {@link Equivalence#equivalent(Object, Object)} applied to the wrapped 1921d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * references is {@code true} and both wrappers use the {@link Object#equals(Object) same} 1931d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * equivalence. 1941d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 1951d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override public boolean equals(@Nullable Object obj) { 1961d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert if (obj == this) { 1971d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return true; 1981d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } else if (obj instanceof Wrapper) { 1991d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert Wrapper<?> that = (Wrapper<?>) obj; 2001d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /* 2011d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * We cast to Equivalence<Object> here because we can't check the type of the reference held 2021d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * by the other wrapper. But, by checking that the Equivalences are equal, we know that 2031d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * whatever type it is, it is assignable to the type handled by this wrapper's equivalence. 2041d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 2051d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @SuppressWarnings("unchecked") 2061d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert Equivalence<Object> equivalence = (Equivalence<Object>) this.equivalence; 2071d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return equivalence.equals(that.equivalence) 2081d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert && equivalence.equivalent(this.reference, that.reference); 2091d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } else { 2101d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return false; 2111d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 2121d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 2131d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 2141d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 2151d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Returns the result of {@link Equivalence#hash(Object)} applied to the the wrapped reference. 2161d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 2171d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override public int hashCode() { 2181d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return equivalence.hash(reference); 2191d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 2201d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 2211d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 2221d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Returns a string representation for this equivalence wrapper. The form of this string 2231d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * representation is not specified. 2241d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 2251d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override public String toString() { 2261d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return equivalence + ".wrap(" + reference + ")"; 2271d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 2281d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 2291d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert private static final long serialVersionUID = 0; 2301d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 2311d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 2321d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 2331d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Returns an equivalence over iterables based on the equivalence of their elements. More 2341d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * specifically, two iterables are considered equivalent if they both contain the same number of 2351d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * elements, and each pair of corresponding elements is equivalent according to 2361d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * {@code this}. Null iterables are equivalent to one another. 2371d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 2381d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * <p>Note that this method performs a similar function for equivalences as {@link 2391d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * com.google.common.collect.Ordering#lexicographical} does for orderings. 2401d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 2411d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 10.0 2421d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 2431d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @GwtCompatible(serializable = true) 2441d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public final <S extends T> Equivalence<Iterable<S>> pairwise() { 2451d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert // Ideally, the returned equivalence would support Iterable<? extends T>. However, 2461d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert // the need for this is so rare that it's not worth making callers deal with the ugly wildcard. 2471d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return new PairwiseEquivalence<S>(this); 2481d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 2491d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 2501d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert /** 2511d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Returns a predicate that evaluates to true if and only if the input is 2521d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * equivalent to {@code target} according to this equivalence relation. 2531d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * 2541d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 10.0 2551d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert */ 2561d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert public final Predicate<T> equivalentTo(@Nullable T target) { 2571d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return new EquivalentToPredicate<T>(this, target); 2581d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 2591d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 2601d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert private static final class EquivalentToPredicate<T> implements Predicate<T>, Serializable { 2611d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 2621d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert private final Equivalence<T> equivalence; 2631d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Nullable private final T target; 2641d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 2651d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert EquivalentToPredicate(Equivalence<T> equivalence, @Nullable T target) { 2661d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert this.equivalence = checkNotNull(equivalence); 2671d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert this.target = target; 2681d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 2691d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 2701d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override public boolean apply(@Nullable T input) { 2711d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return equivalence.equivalent(input, target); 2721d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 2731d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 2741d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override public boolean equals(@Nullable Object obj) { 2751d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert if (this == obj) { 2761d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return true; 2771d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 2781d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert if (obj instanceof EquivalentToPredicate) { 2791d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert EquivalentToPredicate<?> that = (EquivalentToPredicate<?>) obj; 2801d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return equivalence.equals(that.equivalence) 2811d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert && Objects.equal(target, that.target); 2821d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 2831d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return false; 2841d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 2851d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 2861d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override public int hashCode() { 2871d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return Objects.hashCode(equivalence, target); 2881d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 2891d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 2901d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert @Override public String toString() { 2911d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert return equivalence + ".equivalentTo(" + target + ")"; 2921d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 2931d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert 2941d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert private static final long serialVersionUID = 0; 2951d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert } 2961d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert} 297