1 /*
2 * (c) Copyright 2006-2020 by rapiddweller GmbH & Volker Bergmann. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, is permitted under the terms of the
6 * GNU General Public License.
7 *
8 * For redistributing this software or a derivative work under a license other
9 * than the GPL-compatible Free Software License as defined by the Free
10 * Software Foundation or approved by OSI, you must first obtain a commercial
11 * license to this software product from rapiddweller GmbH & Volker Bergmann.
12 *
13 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
14 * WITHOUT A WARRANTY OF ANY KIND. ALL EXPRESS OR IMPLIED CONDITIONS,
15 * REPRESENTATIONS AND WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF
16 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE
17 * HEREBY EXCLUDED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
18 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
19 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
20 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
21 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
22 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
23 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
24 * POSSIBILITY OF SUCH DAMAGE.
25 */
26
27 package com.rapiddweller.benerator.distribution.sequence;
28
29 import com.rapiddweller.benerator.util.RandomUtil;
30
31 import java.util.ArrayList;
32
33 /**
34 * Helper class for the {@link ExpandGeneratorProxy}.
35 * It can buffer a number of values provided from a source and provide a randomly selected one.
36 * The class is optimized for performance: As long as the source is available, the client
37 * can fetch a random value by calling randomElement(E feed) providing a new value from the
38 * source. The {@link ValueBucket} will then select a random element from its buffer, return
39 * it and replace the internal value with the new feed value. When the source is no longer
40 * available, a call to randomElement() will return the last value from the buffer and remove
41 * it (avoiding expensive shift operations that would result from choosing value from a random
42 * position).<br/>
43 * <br/>
44 * Created: 10.12.2009 15:10:33
45 *
46 * @param <E> the type parameter
47 * @author Volker Bergmann
48 * @since 0.6.0
49 */
50 class ValueBucket<E> {
51
52 private final ArrayList<E> buffer;
53
54 /**
55 * Instantiates a new Value bucket.
56 *
57 * @param capacity the capacity
58 */
59 public ValueBucket(int capacity) {
60 buffer = new ArrayList<>();
61 }
62
63 // interface -------------------------------------------------------------------------------------------------------
64
65 /**
66 * Is empty boolean.
67 *
68 * @return the boolean
69 */
70 public boolean isEmpty() {
71 return buffer.isEmpty();
72 }
73
74 /**
75 * Add.
76 *
77 * @param feed the feed
78 */
79 public void add(E feed) {
80 buffer.add(feed);
81 }
82
83 /**
84 * Gets random element.
85 *
86 * @return the random element
87 */
88 public synchronized E getRandomElement() {
89 return buffer.get(RandomUtil.randomIndex(buffer));
90 }
91
92 /**
93 * Gets and replace random element.
94 *
95 * @param feed the feed
96 * @return the and replace random element
97 */
98 public synchronized E getAndReplaceRandomElement(E feed) {
99 int index = RandomUtil.randomIndex(buffer);
100 E result = buffer.get(index);
101 buffer.set(index, feed);
102 return result;
103 }
104
105 /**
106 * Gets and remove random element.
107 *
108 * @return the and remove random element
109 */
110 public synchronized E getAndRemoveRandomElement() {
111 int lastIndex = buffer.size() - 1;
112 E result = buffer.get(lastIndex);
113 buffer.remove(lastIndex);
114 return result;
115 }
116
117 /**
118 * Size int.
119 *
120 * @return the int
121 */
122 public int size() {
123 return buffer.size();
124 }
125
126 // java.lang.Object overrides --------------------------------------------------------------------------------------
127
128 @Override
129 public String toString() {
130 return getClass().getSimpleName() + buffer;
131 }
132
133 }