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1   /*
2    * $Id: Delta.java 8077 2007-08-27 20:15:25Z aperepel $
3    * --------------------------------------------------------------------------------------
4    * Copyright (c) MuleSource, Inc.  All rights reserved.  http://www.mulesource.com
5    *
6    * The software in this package is published under the terms of the CPAL v1.0
7    * license, a copy of which has been included with this distribution in the
8    * LICENSE.txt file.
9    */
10  
11  package org.mule.util.counters.impl;
12  
13  import org.mule.util.counters.CounterFactory.Type;
14  
15  public class Delta extends AggregateCounter
16  {
17  
18      private double first = 0.0;
19      private double second = 0.0;
20  
21      public Delta(String name, AbstractCounter base)
22      {
23          super(name, Type.DELTA, base);
24      }
25  
26      public double nextValue()
27      {
28          if (Double.isNaN(first) || Double.isNaN(second))
29          {
30              return Double.NaN;
31          }
32          else
33          {
34              return second - first > 0.0 ? second - first : 0.0;
35          }
36      }
37  
38      public void doCompute()
39      {
40          first = second;
41          second = this.getBase().nextValue();
42      }
43  
44  }