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/*
* Copyright (C) 2011 The Guava Authors
*
* 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.
*/
package com.google.common.base;
import static com.google.common.base.Preconditions.checkNotNull;
import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import java.io.Serializable;
import javax.annotation.Nullable;
/**
* Equivalence applied on functional result.
*
* @author Bob Lee
* @since 10.0
*/
@Beta
@GwtCompatible
final class FunctionalEquivalence<F, T> extends Equivalence<F>
implements Serializable {
private static final long serialVersionUID = 0;
private final Function<F, ? extends T> function;
private final Equivalence<T> resultEquivalence;
FunctionalEquivalence(
Function<F, ? extends T> function, Equivalence<T> resultEquivalence) {
this.function = checkNotNull(function);
this.resultEquivalence = checkNotNull(resultEquivalence);
}
@Override protected boolean doEquivalent(F a, F b) {
return resultEquivalence.equivalent(function.apply(a), function.apply(b));
}
@Override protected int doHash(F a) {
return resultEquivalence.hash(function.apply(a));
}
@Override public boolean equals(@Nullable Object obj) {
if (obj == this) {
return true;
}
if (obj instanceof FunctionalEquivalence) {
FunctionalEquivalence<?, ?> that = (FunctionalEquivalence<?, ?>) obj;
return function.equals(that.function)
&& resultEquivalence.equals(that.resultEquivalence);
}
return false;
}
@Override public int hashCode() {
return Objects.hashCode(function, resultEquivalence);
}
@Override public String toString() {
return resultEquivalence + ".onResultOf(" + function + ")";
}
}
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