code: /*
   * Copyright © 2014-2017 EntIT Software LLC, a Micro Focus company (L.P.)
   *
   * 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 io.cloudslang.score.events;
  
  import java.util.Objects;
  
  public class FastEventBusImpl implements FastEventBus {
  
      private UninterruptibleScoreEventListener eventHandler;
  
      public void registerEventListener(UninterruptibleScoreEventListener eventHandler) {
          Objects.requireNonNull(eventHandler, "eventHandler must not be null");
          if (this.eventHandler == null ) {
              this.eventHandler = eventHandler;
          } else {
              StringBuilder errorMessage = new StringBuilder();
              errorMessage.append("Failed to register '").append(eventHandler.getClass().getName())
                      .append("' because another '").append(this.eventHandler.getClass().getName())
                      .append("' is registered. You cannot register more than one eventHandler for FastEventBus.");
              throw new RuntimeException(errorMessage.toString());
          }
      }
  
      public void dispatch(ScoreEvent event) {
          if (eventHandler != null) {
              eventHandler.onEvent(event);
          }
      }
  }
  