1 /*
2  * Copyright (C) 2012 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 
21 import java.util.Comparator;
22 import java.util.Iterator;
23 import java.util.NavigableSet;
24 import java.util.Set;
25 
26 /**
27  * A skeleton implementation of a descending multiset.  Only needs
28  * {@code forwardMultiset()} and {@code entryIterator()}.
29  *
30  * @author Louis Wasserman
31  */
32 @GwtCompatible(emulated = true)
33 abstract class DescendingMultiset<E> extends ForwardingMultiset<E>
34     implements SortedMultiset<E> {
forwardMultiset()35   abstract SortedMultiset<E> forwardMultiset();
36 
37   private transient Comparator<? super E> comparator;
38 
comparator()39   @Override public Comparator<? super E> comparator() {
40     Comparator<? super E> result = comparator;
41     if (result == null) {
42       return comparator =
43           Ordering.from(forwardMultiset().comparator()).<E>reverse();
44     }
45     return result;
46   }
47 
48   private transient NavigableSet<E> elementSet;
49 
elementSet()50   @Override public NavigableSet<E> elementSet() {
51     NavigableSet<E> result = elementSet;
52     if (result == null) {
53       return elementSet = new SortedMultisets.NavigableElementSet<E>(this);
54     }
55     return result;
56   }
57 
pollFirstEntry()58   @Override public Entry<E> pollFirstEntry() {
59     return forwardMultiset().pollLastEntry();
60   }
61 
pollLastEntry()62   @Override public Entry<E> pollLastEntry() {
63     return forwardMultiset().pollFirstEntry();
64   }
65 
headMultiset(E toElement, BoundType boundType)66   @Override public SortedMultiset<E> headMultiset(E toElement,
67       BoundType boundType) {
68     return forwardMultiset().tailMultiset(toElement, boundType)
69         .descendingMultiset();
70   }
71 
subMultiset(E fromElement, BoundType fromBoundType, E toElement, BoundType toBoundType)72   @Override public SortedMultiset<E> subMultiset(E fromElement,
73       BoundType fromBoundType, E toElement, BoundType toBoundType) {
74     return forwardMultiset().subMultiset(toElement, toBoundType, fromElement,
75         fromBoundType).descendingMultiset();
76   }
77 
tailMultiset(E fromElement, BoundType boundType)78   @Override public SortedMultiset<E> tailMultiset(E fromElement,
79       BoundType boundType) {
80     return forwardMultiset().headMultiset(fromElement, boundType)
81         .descendingMultiset();
82   }
83 
delegate()84   @Override protected Multiset<E> delegate() {
85     return forwardMultiset();
86   }
87 
descendingMultiset()88   @Override public SortedMultiset<E> descendingMultiset() {
89     return forwardMultiset();
90   }
91 
firstEntry()92   @Override public Entry<E> firstEntry() {
93     return forwardMultiset().lastEntry();
94   }
95 
lastEntry()96   @Override public Entry<E> lastEntry() {
97     return forwardMultiset().firstEntry();
98   }
99 
entryIterator()100   abstract Iterator<Entry<E>> entryIterator();
101 
102   private transient Set<Entry<E>> entrySet;
103 
entrySet()104   @Override public Set<Entry<E>> entrySet() {
105     Set<Entry<E>> result = entrySet;
106     return (result == null) ? entrySet = createEntrySet() : result;
107   }
108 
createEntrySet()109   Set<Entry<E>> createEntrySet() {
110     return new Multisets.EntrySet<E>() {
111       @Override Multiset<E> multiset() {
112         return DescendingMultiset.this;
113       }
114 
115       @Override public Iterator<Entry<E>> iterator() {
116         return entryIterator();
117       }
118 
119       @Override public int size() {
120         return forwardMultiset().entrySet().size();
121       }
122     };
123   }
124 
125   @Override public Iterator<E> iterator() {
126     return Multisets.iteratorImpl(this);
127   }
128 
129   @Override public Object[] toArray() {
130     return standardToArray();
131   }
132 
133   @Override public <T> T[] toArray(T[] array) {
134     return standardToArray(array);
135   }
136 
137   @Override public String toString() {
138     return entrySet().toString();
139   }
140 }