code: // Licensed to the Software Freedom Conservancy (SFC) under one
  // or more contributor license agreements.  See the NOTICE file
  // distributed with this work for additional information
  // regarding copyright ownership.  The SFC 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.openqa.selenium.events.zeromq;
  
  import java.util.List;
  import java.util.concurrent.CopyOnWriteArrayList;
  import java.util.function.Consumer;
  import org.openqa.selenium.events.Event;
  import org.openqa.selenium.events.EventName;
  import org.openqa.selenium.internal.Require;
  
  class Topic {
  
    private final List<Consumer<Event>> listeners = new CopyOnWriteArrayList<>();
    private final EventName eventName;
  
    Topic(EventName forEventName) {
      this.eventName = Require.nonNull("Type", forEventName);
    }
  
    void addListener(Consumer<Event> listener) {
      listeners.add(Require.nonNull("Event listener", listener));
    }
  
    public void fire(Event event) {
      if (!eventName.equals(event.getType())) {
        return;
      }
  
      listeners.parallelStream().forEach(listener -> listener.accept(event));
    }
  }
  