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 com.alibaba.metrics;
  
  /**
   * An incrementing and decrementing counter metric.
   */
  public class CounterImpl implements Counter {
  
      private final LongAdder count;
  
      public CounterImpl() {
          this.count = new LongAdder();
      }
  
      /**
       * Increment the counter by one.
       */
      public void inc() {
          inc(1);
      }
  
      /**
       * Increment the counter by {@code n}.
       *
       * @param n the amount by which the counter will be increased
       */
      public void inc(long n) {
          count.add(n);
      }
  
      /**
       * Decrement the counter by one.
       */
      public void dec() {
          dec(1);
      }
  
      /**
       * Decrement the counter by {@code n}.
       *
       * @param n the amount by which the counter will be decreased
       */
      public void dec(long n) {
          count.add(-n);
      }
  
      /**
       * Returns the counter's current value.
       *
       * @return the counter's current value
       */
      public long getCount() {
          return count.sum();
      }
  
      /**
       * Implementation notes:
       * Recording the last updated time for each update is very expensive according to JMH benchmark,
       * about 6x slower.
       * Because this implementation is only used internally, so this function just returns 0.
       * @return always return 0.
       */
      @Override
      public long lastUpdateTime() {
          return System.currentTimeMillis();
      }
  }
  