content: /*
   * Copyright (C) 2012 The Guava Authors
   *
   * Licensed 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.aliyun.hitsdb.client.util.guava.base;
  
  /**
   * The implementation of Ticker is derived from the Ticker class of Guava 16.0,
   * which is licensed under the Apache License 2.0
   */
  public abstract class Ticker {
      /**
       * Constructor for use by subclasses.
       */
      protected Ticker() {}
  
      /**
       * Returns the number of nanoseconds elapsed since this ticker's fixed
       * point of reference.
       */
      public abstract long read();
  
      /**
       * A ticker that reads the current time using {@link System#nanoTime}.
       *
       * @since 10.0
       */
      public static Ticker systemTicker() {
          return SYSTEM_TICKER;
      }
  
      /**
       * The original implementation of read() is to return Platform.systemNanoTime()
       * However, it is equivalent with System.nanoTime()
       */
      private static final Ticker SYSTEM_TICKER = new Ticker() {
          @Override
          public long read() {
              return System.nanoTime();
          }
      };
  }
  