Coverage Summary for Class: NullsFirstOrdering (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 com.google.common.annotations.GwtCompatible;
20 import java.io.Serializable;
21 import org.checkerframework.checker.nullness.qual.Nullable;
22 
23 /** An ordering that treats {@code null} as less than all other values. */
24 @GwtCompatible(serializable = true)
25 final class NullsFirstOrdering<T> extends Ordering<T> implements Serializable {
26   final Ordering<? super T> ordering;
27 
28   NullsFirstOrdering(Ordering<? super T> ordering) {
29     this.ordering = ordering;
30   }
31 
32   @Override
33   public int compare(@Nullable T left, @Nullable T right) {
34     if (left == right) {
35       return 0;
36     }
37     if (left == null) {
38       return RIGHT_IS_GREATER;
39     }
40     if (right == null) {
41       return LEFT_IS_GREATER;
42     }
43     return ordering.compare(left, right);
44   }
45 
46   @Override
47   public <S extends T> Ordering<S> reverse() {
48     // ordering.reverse() might be optimized, so let it do its thing
49     return ordering.reverse().nullsLast();
50   }
51 
52   @SuppressWarnings("unchecked") // still need the right way to explain this
53   @Override
54   public <S extends T> Ordering<S> nullsFirst() {
55     return (Ordering<S>) this;
56   }
57 
58   @Override
59   public <S extends T> Ordering<S> nullsLast() {
60     return ordering.nullsLast();
61   }
62 
63   @Override
64   public boolean equals(@Nullable Object object) {
65     if (object == this) {
66       return true;
67     }
68     if (object instanceof NullsFirstOrdering) {
69       NullsFirstOrdering<?> that = (NullsFirstOrdering<?>) object;
70       return this.ordering.equals(that.ordering);
71     }
72     return false;
73   }
74 
75   @Override
76   public int hashCode() {
77     return ordering.hashCode() ^ 957692532; // meaningless
78   }
79 
80   @Override
81   public String toString() {
82     return ordering + ".nullsFirst()";
83   }
84 
85   private static final long serialVersionUID = 0;
86 }