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.beam.sdk.extensions.ordered;
  
  import java.io.Serializable;
  
  /** Mutable state mutates when events apply to it. It is stored in a Beam state. */
  public interface MutableState<EventT, ResultT> extends Serializable {
  
    /**
     * The interface assumes that events will mutate the state without the possibility of throwing an
     * error.
     *
     * @param event to be processed
     * @throws Exception if a checked exception is thrown, the event will be output into {@link
     *     OrderedEventProcessorResult#unprocessedEvents()} with
     */
    void mutate(EventT event) throws Exception;
  
    /**
     * This method is called after each state mutation.
     *
     * @return Result of the processing. Can be null if nothing needs to be output after this
     *     mutation.
     */
    ResultT produceResult();
  }
  