/*
* Copyright (C) 2007 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.collect;
import static com.google.common.base.Preconditions.checkNotNull;
import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Function;
import com.google.common.base.Objects;
import java.io.Serializable;
import javax.annotation.Nullable;
/**
* An ordering that orders elements by applying an order to the result of a
* function on those elements.
*/
@GwtCompatible(serializable = true)
final class ByFunctionOrdering<F, T>
extends Ordering<F> implements Serializable {
final Function<F, ? extends T> function;
final Ordering<T> ordering;
ByFunctionOrdering(
Function<F, ? extends T> function, Ordering<T> ordering) {
this.function = checkNotNull(function);
this.ordering = checkNotNull(ordering);
}
@Override public int compare(F left, F right) {
return ordering.compare(function.apply(left), function.apply(right));
}
@Override public boolean equals(@Nullable Object object) {
if (object == this) {
return true;
}
if (object instanceof ByFunctionOrdering) {
ByFunctionOrdering<?, ?> that = (ByFunctionOrdering<?, ?>) object;
return this.function.equals(that.function)
&& this.ordering.equals(that.ordering);
}
return false;
}
@Override public int hashCode() {
return Objects.hashCode(function, ordering);
}
@Override public String toString() {
return ordering + ".onResultOf(" + function + ")";
}
private static final long serialVersionUID = 0;
}
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