BaseSchemaIdCounter.java

/*
 * Copyright 2014-2016 CyberVision, Inc.
 *
 * 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 org.kaaproject.kaa.server.datamigration.utils;

public class BaseSchemaIdCounter {
  private static BaseSchemaIdCounter instance;
  private static boolean isInitMethodCalled;
  private Long value;

  private BaseSchemaIdCounter() {

  }


  /**
   * Sets init value for counter, can be called only once.
   *
   * @param value the initial value
   */
  public static void setInitValue(Long value) {
    getInstance();
    if (isInitMethodCalled) {
      return;
    }
    isInitMethodCalled = true;
    instance.value = value;
  }


  /**
   * Gets uniq instance.
   */
  public static BaseSchemaIdCounter getInstance() {
    if (instance == null) {
      instance = new BaseSchemaIdCounter();
    }
    return instance;
  }

  /**
   * Return old value and add to one shift.
   *
   * @param shift the shift
   */
  public Long getAndShift(Long shift) {
    Long oldValue = value;
    value += shift;
    return oldValue;
  }

}