1 /* 2 * Copyright (C) 2011 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not 5 * use this file except in compliance with the License. You may obtain a copy 6 * of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 12 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the 13 * License for the specific language governing permissions and limitations under 14 * the License. 15 */ 16 17 package com.google.common.base; 18 19 import static com.google.common.base.Preconditions.checkNotNull; 20 21 import com.google.common.annotations.Beta; 22 import com.google.common.annotations.GwtCompatible; 23 24 import java.io.Serializable; 25 26 import javax.annotation.Nullable; 27 28 /** 29 * Equivalence applied on functional result. 30 * 31 * @author Bob Lee 32 * @since 10.0 33 */ 34 @Beta 35 @GwtCompatible 36 final class FunctionalEquivalence<F, T> extends Equivalence<F> 37 implements Serializable { 38 39 private static final long serialVersionUID = 0; 40 41 private final Function<F, ? extends T> function; 42 private final Equivalence<T> resultEquivalence; 43 44 FunctionalEquivalence( 45 Function<F, ? extends T> function, Equivalence<T> resultEquivalence) { 46 this.function = checkNotNull(function); 47 this.resultEquivalence = checkNotNull(resultEquivalence); 48 } 49 50 @Override protected boolean doEquivalent(F a, F b) { 51 return resultEquivalence.equivalent(function.apply(a), function.apply(b)); 52 } 53 54 @Override protected int doHash(F a) { 55 return resultEquivalence.hash(function.apply(a)); 56 } 57 58 @Override public boolean equals(@Nullable Object obj) { 59 if (obj == this) { 60 return true; 61 } 62 if (obj instanceof FunctionalEquivalence) { 63 FunctionalEquivalence<?, ?> that = (FunctionalEquivalence<?, ?>) obj; 64 return function.equals(that.function) 65 && resultEquivalence.equals(that.resultEquivalence); 66 } 67 return false; 68 } 69 70 @Override public int hashCode() { 71 return Objects.hashCode(function, resultEquivalence); 72 } 73 74 @Override public String toString() { 75 return resultEquivalence + ".onResultOf(" + function + ")"; 76 } 77 } 78
