content: /**
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.activemq.management;
  
  import java.util.concurrent.atomic.AtomicLong;
  
  /**
   * A count statistic implementation
   * 
   * 
   */
  public class CountStatisticImpl extends StatisticImpl implements CountStatistic {
  
      private final AtomicLong counter = new AtomicLong(0);
      private CountStatisticImpl parent;
  
      public CountStatisticImpl(CountStatisticImpl parent, String name, String description) {
          this(name, description);
          this.parent = parent;
      }
  
      public CountStatisticImpl(String name, String description) {
          this(name, "count", description);
      }
  
      public CountStatisticImpl(String name, String unit, String description) {
          super(name, unit, description);
      }
  
      public void reset() {
          if (isDoReset()) {
              super.reset();
              counter.set(0);
          }
      }
  
      public long getCount() {
          return counter.get();
      }
  
      public void setCount(long count) {
          if (isEnabled()) {
              counter.set(count);
          }
      }
  
      public void add(long amount) {
          if (isEnabled()) {
              counter.addAndGet(amount);
              updateSampleTime();
              if (parent != null) {
                  parent.add(amount);
              }
          }
      }
  
      public void increment() {
          if (isEnabled()) {
              counter.incrementAndGet();
              updateSampleTime();
              if (parent != null) {
                  parent.increment();
              }
          }
      }
  
      public void subtract(long amount) {
          if (isEnabled()) {
              counter.addAndGet(-amount);
              updateSampleTime();
              if (parent != null) {
                  parent.subtract(amount);
              }
          }
      }
  
      public void decrement() {
          if (isEnabled()) {
              counter.decrementAndGet();
              updateSampleTime();
              if (parent != null) {
                  parent.decrement();
              }
          }
      }
  
      public CountStatisticImpl getParent() {
          return parent;
      }
  
      public void setParent(CountStatisticImpl parent) {
          if (this.parent != null) {
              this.parent.subtract(this.getCount());
          }
          this.parent = parent;
      }
  
      protected void appendFieldDescription(StringBuffer buffer) {
          buffer.append(" count: ");
          buffer.append(Long.toString(counter.get()));
          super.appendFieldDescription(buffer);
      }
  
      /**
       * @return the average time period that elapses between counter increments
       *         since the last reset.
       */
      public double getPeriod() {
          double count = counter.get();
          if (count == 0) {
              return 0;
          }
          double time = System.currentTimeMillis() - getStartTime();
          return time / (count * 1000.0);
      }
  
      /**
       * @return the number of times per second that the counter is incrementing
       *         since the last reset.
       */
      public double getFrequency() {
          double count = counter.get();
          double time = System.currentTimeMillis() - getStartTime();
          return count * 1000.0 / time;
      }
  
  }
  