Atomics.java example

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/*
 * 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.geode.internal.concurrent;

import org.apache.geode.Statistics;
import org.apache.geode.StatisticsType;
import org.apache.geode.distributed.internal.DistributionConfig;
import org.apache.geode.internal.statistics.LocalStatisticsImpl;
import org.apache.geode.internal.statistics.StatisticsManager;
import org.apache.geode.internal.statistics.StatisticsTypeImpl;
import org.apache.geode.internal.stats50.Atomic50StatisticsImpl;

import java.util.concurrent.atomic.AtomicLong;

public class Atomics {
  private Atomics() {}

  /**
   * Whether per-thread stats are used. Striping is disabled for the IBM JVM due to bug 38226
   */
  private static final boolean STRIPED_STATS_DISABLED =
      Boolean.getBoolean(DistributionConfig.GEMFIRE_PREFIX + "STRIPED_STATS_DISABLED")
          || "IBM Corporation".equals(System.getProperty("java.vm.vendor", "unknown"));


  public static Statistics createAtomicStatistics(StatisticsType type, String textId, long nId,
      long uId, StatisticsManager mgr) {
    Statistics result = null;
    if (((StatisticsTypeImpl) type).getDoubleStatCount() == 0 && !STRIPED_STATS_DISABLED) {
      result = new Atomic50StatisticsImpl(type, textId, nId, uId, mgr);
    } else {
      result = new LocalStatisticsImpl(type, textId, nId, uId, true, 0, mgr);
    }
    return result;
  }

  /**
   * Use it only when threads are doing incremental updates. If updates are random then this method
   * may not be optimal.
   */
  public static boolean setIfGreater(AtomicLong atom, long update) {
    while (true) {
      long cur = atom.get();

      if (update > cur) {
        if (atom.compareAndSet(cur, update))
          return true;
      } else
        return false;
    }
  }
}