/
FunctionalEquivalence.java
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/
FunctionalEquivalence.java
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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.GwtCompatible;
import java.io.Serializable;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* Equivalence applied on functional result.
*
* @author Bob Lee
* @since 10.0
*/
@GwtCompatible
@ElementTypesAreNonnullByDefault
final class FunctionalEquivalence<F, T> extends Equivalence<F> implements Serializable {
private static final long serialVersionUID = 0;
private final Function<? super F, ? extends @Nullable T> function;
private final Equivalence<T> resultEquivalence;
FunctionalEquivalence(
Function<? super F, ? extends @Nullable 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(@CheckForNull 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 + ")";
}
}