1 /**
2 * Redistribution and use in source and binary forms, with or without
3 * modification, are permitted provided that the following conditions are
4 * met :
5 *
6 * . Redistributions of source code must retain the above copyright
7 * notice, this list of conditions and the following disclaimer.
8 *
9 * . Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * . The name of the author may not be used to endorse or promote products
14 * derived from this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
18 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
19 * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
20 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
21 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
22 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
24 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
25 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
26 * POSSIBILITY OF SUCH DAMAGE.
27 */
28
29 package cppncss.measure;
30
31 /**
32 * Computes the average of a series of values.
33 *
34 * @author Mathieu Champlon
35 */
36 public final class Average
37 {
38 private final String label;
39 private float average;
40 private float count;
41
42 /**
43 * Create an average.
44 *
45 * @param label the label of the measurement
46 * @param value the first value of the measurement
47 */
48 public Average( final String label, final int value )
49 {
50 this.label = label;
51 this.average = value;
52 this.count = 1;
53 }
54
55 /**
56 * Add a value to the average and recompute it.
57 * <p>
58 * If the label does not match the label given at creation the measurement is ignored.
59 *
60 * @param label the label of the measurement
61 * @param value the value of the measurement
62 * @return whether the measurement has been accepted or not
63 */
64 public boolean update( final String label, final int value )
65 {
66 if( !this.label.equals( label ) )
67 return false;
68 average = (average * count + value) / (count + 1);
69 ++count;
70 return true;
71 }
72
73 /**
74 * Accept a visitor.
75 *
76 * @param observer an average observer
77 */
78 public void accept( final AverageObserver observer )
79 {
80 observer.notify( label, average );
81 }
82 }