1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.collections.primitives;
18
19 import org.apache.commons.collections.primitives.decorators.UnmodifiableIntIterator;
20 import org.apache.commons.collections.primitives.decorators.UnmodifiableIntList;
21 import org.apache.commons.collections.primitives.decorators.UnmodifiableIntListIterator;
22
23 /**
24 * This class consists exclusively of static methods that operate on or
25 * return IntCollections.
26 * <p>
27 * The methods of this class all throw a NullPointerException if the
28 * provided collection is null.
29 *
30 * @version $Revision: 480460 $ $Date: 2006-11-29 03:14:21 -0500 (Wed, 29 Nov 2006) $
31 *
32 * @author Rodney Waldhoff
33 */
34 public final class IntCollections {
35
36 /**
37 * Returns an unmodifiable IntList containing only the specified element.
38 * @param value the single value
39 * @return an unmodifiable IntList containing only the specified element.
40 */
41 public static IntList singletonIntList(int value) {
42 // TODO: a specialized implementation of IntList may be more performant
43 IntList list = new ArrayIntList(1);
44 list.add(value);
45 return UnmodifiableIntList.wrap(list);
46 }
47
48 /**
49 * Returns an unmodifiable IntIterator containing only the specified element.
50 * @param value the single value
51 * @return an unmodifiable IntIterator containing only the specified element.
52 */
53 public static IntIterator singletonIntIterator(int value) {
54 return singletonIntList(value).iterator();
55 }
56
57 /**
58 * Returns an unmodifiable IntListIterator containing only the specified element.
59 * @param value the single value
60 * @return an unmodifiable IntListIterator containing only the specified element.
61 */
62 public static IntListIterator singletonIntListIterator(int value) {
63 return singletonIntList(value).listIterator();
64 }
65
66 /**
67 * Returns an unmodifiable version of the given non-null IntList.
68 * @param list the non-null IntList to wrap in an unmodifiable decorator
69 * @return an unmodifiable version of the given non-null IntList
70 * @throws NullPointerException if the given IntList is null
71 * @see org.apache.commons.collections.primitives.decorators.UnmodifiableIntList#wrap
72 */
73 public static IntList unmodifiableIntList(IntList list) throws NullPointerException {
74 if(null == list) {
75 throw new NullPointerException();
76 }
77 return UnmodifiableIntList.wrap(list);
78 }
79
80 /**
81 * Returns an unmodifiable version of the given non-null IntIterator.
82 * @param iter the non-null IntIterator to wrap in an unmodifiable decorator
83 * @return an unmodifiable version of the given non-null IntIterator
84 * @throws NullPointerException if the given IntIterator is null
85 * @see org.apache.commons.collections.primitives.decorators.UnmodifiableIntIterator#wrap
86 */
87 public static IntIterator unmodifiableIntIterator(IntIterator iter) {
88 if(null == iter) {
89 throw new NullPointerException();
90 }
91 return UnmodifiableIntIterator.wrap(iter);
92 }
93
94 /**
95 * Returns an unmodifiable version of the given non-null IntListIterator.
96 * @param iter the non-null IntListIterator to wrap in an unmodifiable decorator
97 * @return an unmodifiable version of the given non-null IntListIterator
98 * @throws NullPointerException if the given IntListIterator is null
99 * @see org.apache.commons.collections.primitives.decorators.UnmodifiableIntListIterator#wrap
100 */
101 public static IntListIterator unmodifiableIntListIterator(IntListIterator iter) {
102 if(null == iter) {
103 throw new NullPointerException();
104 }
105 return UnmodifiableIntListIterator.wrap(iter);
106 }
107
108 /**
109 * Returns an unmodifiable, empty IntList.
110 * @return an unmodifiable, empty IntList.
111 * @see #EMPTY_INT_LIST
112 */
113 public static IntList getEmptyIntList() {
114 return EMPTY_INT_LIST;
115 }
116
117 /**
118 * Returns an unmodifiable, empty IntIterator
119 * @return an unmodifiable, empty IntIterator.
120 * @see #EMPTY_INT_ITERATOR
121 */
122 public static IntIterator getEmptyIntIterator() {
123 return EMPTY_INT_ITERATOR;
124 }
125
126 /**
127 * Returns an unmodifiable, empty IntListIterator
128 * @return an unmodifiable, empty IntListIterator.
129 * @see #EMPTY_INT_LIST_ITERATOR
130 */
131 public static IntListIterator getEmptyIntListIterator() {
132 return EMPTY_INT_LIST_ITERATOR;
133 }
134
135 /**
136 * An unmodifiable, empty IntList
137 * @see #getEmptyIntList
138 */
139 public static final IntList EMPTY_INT_LIST = unmodifiableIntList(new ArrayIntList(0));
140
141 /**
142 * An unmodifiable, empty IntIterator
143 * @see #getEmptyIntIterator
144 */
145 public static final IntIterator EMPTY_INT_ITERATOR = unmodifiableIntIterator(EMPTY_INT_LIST.iterator());
146
147 /**
148 * An unmodifiable, empty IntListIterator
149 * @see #getEmptyIntListIterator
150 */
151 public static final IntListIterator EMPTY_INT_LIST_ITERATOR = unmodifiableIntListIterator(EMPTY_INT_LIST.listIterator());
152 }