| /* |
| * 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; |
| import org.checkerframework.checker.nullness.compatqual.NullableDecl; |
| |
| /** 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<Comparable> implements Serializable { |
| static final NaturalOrdering INSTANCE = new NaturalOrdering(); |
| |
| @NullableDecl private transient Ordering<Comparable> nullsFirst; |
| @NullableDecl private transient Ordering<Comparable> nullsLast; |
| |
| @Override |
| public int compare(Comparable left, Comparable right) { |
| checkNotNull(left); // for GWT |
| checkNotNull(right); |
| return left.compareTo(right); |
| } |
| |
| @Override |
| public <S extends Comparable> Ordering<S> nullsFirst() { |
| Ordering<Comparable> result = nullsFirst; |
| if (result == null) { |
| result = nullsFirst = super.nullsFirst(); |
| } |
| return (Ordering<S>) result; |
| } |
| |
| @Override |
| public <S extends Comparable> Ordering<S> nullsLast() { |
| Ordering<Comparable> result = nullsLast; |
| if (result == null) { |
| result = nullsLast = super.nullsLast(); |
| } |
| return (Ordering<S>) result; |
| } |
| |
| @Override |
| public <S extends Comparable> Ordering<S> reverse() { |
| return (Ordering<S>) 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; |
| } |