1 /***
2 * Copyright 2003-2010 Terracotta, Inc.
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 net.sf.ehcache.search.aggregator;
18
19 import net.sf.ehcache.search.Attribute;
20
21 /***
22 * Compute the average (arithmetic mean) as a double
23 *
24 * @author teck
25 */
26 public class Average implements AggregatorInstance<Double> {
27
28 private final Attribute<?> attribute;
29
30 private Engine engine;
31
32 /***
33 * @param attribute
34 */
35 public Average(Attribute<?> attribute) {
36 this.attribute = attribute;
37 }
38
39 /***
40 * {@inheritDoc}
41 * <p/>
42 * NOTE: Null values are ignored and not included in the computation
43 */
44 public void accept(Object input) throws AggregatorException {
45 if (input == null) {
46 return;
47 }
48
49 if (input instanceof Number) {
50 if (engine == null) {
51 engine = Engine.create((Number) input);
52 } else {
53 engine.accept((Number) input);
54 }
55 } else {
56 throw new AggregatorException("Non-number type encounted: " + input.getClass());
57 }
58 }
59
60 /***
61 * {@inheritDoc}
62 * <p/>
63 * NOTE: null is returned if there was no input supplied to this function
64 */
65 public Number aggregateResult() {
66 if (engine == null) {
67 return null;
68 } else {
69 return engine.result();
70 }
71 }
72
73 /***
74 * {@inheritDoc}
75 */
76 public Attribute getAttribute() {
77 return attribute;
78 }
79
80 /***
81 * Abstract super-class for all average calculating engines.
82 */
83 abstract static class Engine {
84
85 /***
86 * Create a type specific engine using the given initial value.
87 *
88 * @param value initial value
89 * @return type specific engine
90 */
91 static Engine create(Number value) {
92 if (value instanceof Float) {
93 return new FloatEngine(value.floatValue());
94 } else if (value instanceof Double) {
95 return new DoubleEngine(value.doubleValue());
96 } else if (value instanceof Long) {
97 return new LongEngine(value.longValue());
98 } else {
99 return new IntegerEngine(value.intValue());
100 }
101 }
102
103 /***
104 * Update the engine with the given value.
105 *
106 * @param input data value
107 */
108 abstract void accept(Number input) throws AggregatorException;
109
110 /***
111 * Get the (current) result of this engine.
112 *
113 * @return engine result
114 */
115 abstract Number result();
116
117 /***
118 * An int based averaging engine.
119 */
120 static class IntegerEngine extends Engine {
121
122 private int count;
123 private long sum;
124
125 /***
126 * Creates a new instance starting with an initial value
127 *
128 * @param value initial value
129 */
130 IntegerEngine(int value) {
131 this.count = 1;
132 this.sum = value;
133 }
134
135 @Override
136 void accept(Number input) throws AggregatorException {
137 count++;
138 sum += input.intValue();
139 }
140
141 @Override
142 Number result() {
143 return Float.valueOf(((float) sum) / count);
144 }
145 }
146
147 /***
148 * A long based averaging engine.
149 */
150 static class LongEngine extends Engine {
151
152 private int count;
153 private long sum;
154
155 /***
156 * Creates a new instance starting with an initial value
157 *
158 * @param value initial value
159 */
160 LongEngine(long value) {
161 this.count = 1;
162 this.sum = value;
163 }
164
165 @Override
166 void accept(Number input) throws AggregatorException {
167 count++;
168 sum += input.longValue();
169 }
170
171 @Override
172 Number result() {
173 return Double.valueOf(((double) sum) / count);
174 }
175 }
176
177 /***
178 * A float based averaging engine.
179 */
180 static class FloatEngine extends Engine {
181
182 private int count;
183 private float sum;
184
185 /***
186 * Creates a new instance starting with an initial value
187 *
188 * @param value initial value
189 */
190 FloatEngine(float value) {
191 this.count = 1;
192 this.sum = value;
193 }
194
195 @Override
196 void accept(Number input) throws AggregatorException {
197 count++;
198 sum += input.floatValue();
199 }
200
201 @Override
202 Number result() {
203 return Float.valueOf(sum / count);
204 }
205 }
206
207 /***
208 * A double based averaging engine.
209 */
210 static class DoubleEngine extends Engine {
211
212 private int count;
213 private double sum;
214
215 /***
216 * Creates a new instance starting with an initial value
217 *
218 * @param value initial value
219 */
220 DoubleEngine(double value) {
221 this.count = 1;
222 this.sum = value;
223 }
224
225 @Override
226 void accept(Number input) throws AggregatorException {
227 count++;
228 sum += input.doubleValue();
229 }
230
231 @Override
232 Number result() {
233 return Double.valueOf(sum / count);
234 }
235 }
236 }
237 }