Coverage Summary for Class: NaturalOrdering (com.google.common.collect)

1 /*
2  * Copyright (C) 2007 The Guava Authors
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package com.google.common.collect;
18 
19 import static com.google.common.base.Preconditions.checkNotNull;
20 
21 import com.google.common.annotations.GwtCompatible;
22 import java.io.Serializable;
23 import org.checkerframework.checker.nullness.qual.Nullable;
24 
25 /** An ordering that uses the natural order of the values. */
26 @GwtCompatible(serializable = true)
27 @SuppressWarnings({"unchecked", "rawtypes"}) // TODO(kevinb): the right way to explain this??
28 final class NaturalOrdering extends Ordering<Comparable> implements Serializable {
29   static final NaturalOrdering INSTANCE = new NaturalOrdering();
30 
31   private transient @Nullable Ordering<Comparable> nullsFirst;
32   private transient @Nullable Ordering<Comparable> nullsLast;
33 
34   @Override
35   public int compare(Comparable left, Comparable right) {
36     checkNotNull(left); // for GWT
37     checkNotNull(right);
38     return left.compareTo(right);
39   }
40 
41   @Override
42   public <S extends Comparable> Ordering<S> nullsFirst() {
43     Ordering<Comparable> result = nullsFirst;
44     if (result == null) {
45       result = nullsFirst = super.nullsFirst();
46     }
47     return (Ordering<S>) result;
48   }
49 
50   @Override
51   public <S extends Comparable> Ordering<S> nullsLast() {
52     Ordering<Comparable> result = nullsLast;
53     if (result == null) {
54       result = nullsLast = super.nullsLast();
55     }
56     return (Ordering<S>) result;
57   }
58 
59   @Override
60   public <S extends Comparable> Ordering<S> reverse() {
61     return (Ordering<S>) ReverseNaturalOrdering.INSTANCE;
62   }
63 
64   // preserving singleton-ness gives equals()/hashCode() for free
65   private Object readResolve() {
66     return INSTANCE;
67   }
68 
69   @Override
70   public String toString() {
71     return "Ordering.natural()";
72   }
73 
74   private NaturalOrdering() {}
75 
76   private static final long serialVersionUID = 0;
77 }