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.grid.config;
  
  import com.google.common.collect.ImmutableList;
  import org.openqa.selenium.json.Json;
  
  import java.util.List;
  import java.util.Map;
  import java.util.Optional;
  import java.util.Set;
  import java.util.logging.Logger;
  
  public interface Config {
  
    Set<String> getSectionNames();
  
    Set<String> getOptions(String section);
  
    Optional<List<String>> getAll(String section, String option);
  
    default Optional<String> get(String section, String option) {
      return getAll(section, option).map(items -> items.isEmpty() ? null : items.get(0));
    }
  
    default Optional<Integer> getInt(String section, String option) {
      return get(section, option).map(Integer::parseInt);
    }
  
    default Optional<Boolean> getBool(String section, String option) {
      return get(section, option).map(Boolean::parseBoolean);
    }
  
    default <X> X getClass(String section, String option, Class<X> typeOfClass, String defaultClazz) {
      String clazz = get(section, option).orElse(defaultClazz);
  
      // We don't declare a constant on the interface, natch.
      Logger.getLogger(Config.class.getName())
          .fine(String.format("Creating %s as instance of %s", clazz, typeOfClass));
  
      try {
        return ClassCreation.callCreateMethod(clazz, typeOfClass, this);
      } catch (ReflectiveOperationException e) {
        throw new IllegalArgumentException("Unable to find class: " + clazz, e);
      }
    }
  
    default List<String> toEntryList(Map<String, Object> mapItem) {
      return mapItem.entrySet().stream()
        .map(entry -> {
          return String.format("%s=%s", entry.getKey(), toJson(entry.getValue()));
        })
        .sorted()
        .collect(ImmutableList.toImmutableList());
    }
  
    default String toJson(Object value) {
      StringBuilder jsonStr = new StringBuilder();
      new Json().newOutput(jsonStr).setPrettyPrint(false).write(value);
      return jsonStr.toString();
    }
  }
  