code: /**
   * Copyright (c) 2016 YCSB Contributors All rights reserved.
   *
   * 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. See accompanying
   * LICENSE file.
   */
  
  package com.yahoo.ycsb.generator;
  
  import java.util.concurrent.atomic.AtomicInteger;
  
  /**
   * Generates a sequence of integers 0, 1, ...
   */
  public class SequentialGenerator extends NumberGenerator {
    final AtomicInteger counter;
    int _interval, _countstart;
  
    /**
     * Create a counter that starts at countstart.
     */
    public SequentialGenerator(int countstart, int countend) {
      counter = new AtomicInteger();
      setLastValue(counter.get());
      _countstart = countstart;
      _interval = countend - countstart + 1;
    }
    
    /**
     * If the generator returns numeric (integer) values, return the next value as an int.
     * Default is to return -1, which is appropriate for generators that do not return numeric values.
     */
    public int nextInt() {
      int ret = _countstart + counter.getAndIncrement() % _interval;
      setLastValue(ret);
      return ret;
    }
    
    @Override
    public Number nextValue() {
      int ret = _countstart + counter.getAndIncrement() % _interval;
      setLastValue(ret);
      return ret;
    }
    
    @Override
    public Number lastValue() {
      return counter.get() + 1;
    }
    
    @Override
    public double mean() {
      throw new UnsupportedOperationException("Can't compute mean of non-stationary distribution!");
    }
  }
  