content: /*
   * 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.kafka.streams.kstream;
  
  
  /**
   * The interface for merging aggregate values for {@link SessionWindows} with the given key.
   *
   * @param <K>   key type
   * @param <V>   aggregate value type
   */
  @FunctionalInterface
  public interface Merger<K, V> {
  
      /**
       * Compute a new aggregate from the key and two aggregates.
       *
       * @param aggKey    the key of the record
       * @param aggOne    the first aggregate
       * @param aggTwo    the second aggregate
       * @return          the new aggregate value
       */
      V apply(final K aggKey, final V aggOne, final V aggTwo);
  }
  