com.google.common.collect.NaturalOrdering Maven / Gradle / Ivy
/*
* 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 java.io.Serializable;
/** An ordering that uses the natural order of the values. */
@GwtCompatible(serializable = true)
@SuppressWarnings({"unchecked", "rawtypes"}) // TODO(kevinb): the right way to explain this??
final class NaturalOrdering extends Ordering implements Serializable {
static final NaturalOrdering INSTANCE = new NaturalOrdering();
private transient Ordering nullsFirst;
private transient Ordering nullsLast;
@Override
public int compare(Comparable left, Comparable right) {
checkNotNull(left); // for GWT
checkNotNull(right);
return left.compareTo(right);
}
@Override
public Ordering nullsFirst() {
Ordering result = nullsFirst;
if (result == null) {
result = nullsFirst = super.nullsFirst();
}
return (Ordering) result;
}
@Override
public Ordering nullsLast() {
Ordering result = nullsLast;
if (result == null) {
result = nullsLast = super.nullsLast();
}
return (Ordering) result;
}
@Override
public Ordering reverse() {
return (Ordering) ReverseNaturalOrdering.INSTANCE;
}
// preserving singleton-ness gives equals()/hashCode() for free
private Object readResolve() {
return INSTANCE;
}
@Override
public String toString() {
return "Ordering.natural()";
}
private NaturalOrdering() {}
private static final long serialVersionUID = 0;
}