library/src/main/java/org/apache/apex/malhar/lib/dimensions/aggregator/AggregatorOTFType.java

/**
 * 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.apex.malhar.lib.dimensions.aggregator;

import java.util.Collections;
import java.util.Map;

import com.google.common.base.Preconditions;
import com.google.common.collect.Maps;

/**
 * This is a convenience enum to store all the information about default {@link OTFAggregator}s
 * in one place.
 *
 * @since 3.1.0
 */
public enum AggregatorOTFType
{
  /**
   * The average {@link OTFAggregator}.
   */
  AVG(AggregatorAverage.INSTANCE);

  /**
   * A map from {@link OTFAggregator} names to {@link OTFAggregator}s.
   */
  public static final Map<String, OTFAggregator> NAME_TO_AGGREGATOR;

  static {
    Map<String, OTFAggregator> nameToAggregator = Maps.newHashMap();

    for (AggregatorOTFType aggType : AggregatorOTFType.values()) {
      nameToAggregator.put(aggType.name(), aggType.getAggregator());
    }

    NAME_TO_AGGREGATOR = Collections.unmodifiableMap(nameToAggregator);
  }

  /**
   * The {@link OTFAggregator} assigned to this enum.
   */
  private OTFAggregator aggregator;

  /**
   * Creates an {@link OTFAggregator} enum with the given aggregator.
   *
   * @param aggregator The {@link OTFAggregator} assigned to this enum.
   */
  AggregatorOTFType(OTFAggregator aggregator)
  {
    setAggregator(aggregator);
  }

  /**
   * Sets the {@link OTFAggregator} assigned to this enum.
   *
   * @param aggregator The {@link OTFAggregator} assigned to this enum.
   */
  private void setAggregator(OTFAggregator aggregator)
  {
    this.aggregator = Preconditions.checkNotNull(aggregator);
  }

  /**
   * Gets the {@link OTFAggregator} assigned to this enum.
   *
   * @return The {@link OTFAggregator} assigned to this enum.
   */
  public OTFAggregator getAggregator()
  {
    return aggregator;
  }
}