blob: d15fbcff77a6d935647a35dea22462d439056c7d (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
|
/*
* Copyright 2006-2012 Amazon Technologies, Inc. or its affiliates.
* Amazon, Amazon.com and Carbonado are trademarks or registered trademarks
* of Amazon Technologies, Inc. or its affiliates. All rights reserved.
*
* 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.amazon.carbonado.cursor;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.NoSuchElementException;
import com.amazon.carbonado.Cursor;
/**
* Special cursor implementation that returns only one element.
*
* @author Brian S O'Neill
* @see EmptyCursor
*/
public class SingletonCursor<S> implements Cursor<S> {
private volatile S mObject;
/**
* @param object single object to return from cursor, must not be null
* @throws IllegalArgumentException if object is null
*/
public SingletonCursor(S object) {
if (object == null) {
throw new IllegalArgumentException();
}
mObject = object;
}
public void close() {
mObject = null;
}
public boolean hasNext() {
return mObject != null;
}
public S next() {
S object = mObject;
mObject = null;
if (object == null) {
throw new NoSuchElementException();
}
return object;
}
public int skipNext(int amount) {
if (amount <= 0) {
if (amount < 0) {
throw new IllegalArgumentException("Cannot skip negative amount: " + amount);
}
return 0;
}
S object = mObject;
mObject = null;
return object == null ? 0 : 1;
}
public int copyInto(Collection<? super S> c) {
S object = mObject;
mObject = null;
if (object == null) {
return 0;
}
c.add(object);
return 1;
}
public int copyInto(Collection<? super S> c, int limit) {
return limit <= 0 ? 0 : copyInto(c);
}
public List<S> toList() {
List<S> list = new ArrayList<S>(1);
copyInto(list);
return list;
}
public List<S> toList(int limit) {
List<S> list = new ArrayList<S>(1);
copyInto(list, limit);
return list;
}
}
|
