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