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 java.util.Arrays;
  import java.util.List;
  import java.util.Map;
  import java.util.Optional;
  import java.util.Set;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.atomic.AtomicReference;
  import org.openqa.selenium.internal.Require;
  
  public class MemoizedConfig implements Config {
  
    private final Config delegate;
  
    private final Map<Key, Optional<Boolean>> seenBools = new ConcurrentHashMap<>();
    private final Map<Key, Object> seenClasses = new ConcurrentHashMap<>();
    private final Map<Key, Optional<Integer>> seenInts = new ConcurrentHashMap<>();
    private final Map<Key, Optional<String>> seenStrings = new ConcurrentHashMap<>();
    private final Map<Key, Optional<List<String>>> seenOptions = new ConcurrentHashMap<>();
  
    public MemoizedConfig(Config delegate) {
      this.delegate = Require.nonNull("Delegate config", delegate);
    }
  
    @Override
    public Set<String> getSectionNames() {
      return delegate.getSectionNames();
    }
  
    @Override
    public Set<String> getOptions(String section) {
      Require.nonNull("Section name", section);
      return delegate.getOptions(section);
    }
  
    @Override
    public Optional<List<String>> getAll(String section, String option) {
      Require.nonNull("Section name", section);
      Require.nonNull("Option", option);
  
      return seenOptions.computeIfAbsent(
          new Key(section, option), ignored -> delegate.getAll(section, option));
    }
  
    @Override
    public Optional<String> get(String section, String option) {
      Require.nonNull("Section name", section);
      Require.nonNull("Option", option);
  
      return seenStrings.computeIfAbsent(
          new Key(section, option), ignored -> delegate.get(section, option));
    }
  
    @Override
    public Optional<Integer> getInt(String section, String option) {
      Require.nonNull("Section name", section);
      Require.nonNull("Option", option);
  
      return seenInts.computeIfAbsent(
          new Key(section, option), ignored -> delegate.getInt(section, option));
    }
  
    @Override
    public Optional<Boolean> getBool(String section, String option) {
      Require.nonNull("Section name", section);
      Require.nonNull("Option", option);
  
      return seenBools.computeIfAbsent(
          new Key(section, option), ignored -> delegate.getBool(section, option));
    }
  
    @Override
    public <X> X getClass(String section, String option, Class<X> typeOfX, String defaultClassName) {
      Require.nonNull("Section name", section);
      Require.nonNull("Option", option);
      Require.nonNull("Type to load", typeOfX);
      Require.nonNull("Default class name", defaultClassName);
  
      AtomicReference<Exception> thrown = new AtomicReference<>();
      Object value =
          seenClasses.computeIfAbsent(
              new Key(section, option, typeOfX.toGenericString(), defaultClassName),
              ignored -> {
                try {
                  String clazz = delegate.get(section, option).orElse(defaultClassName);
                  return ClassCreation.callCreateMethod(clazz, typeOfX, this);
                } catch (Exception e) {
                  thrown.set(e);
                  return null;
                }
              });
  
      if (value != null) {
        return typeOfX.cast(value);
      }
  
      Exception exception = thrown.get();
      if (exception instanceof RuntimeException) {
        throw (RuntimeException) exception;
      }
      throw new ConfigException(exception);
    }
  
    private static class Key {
      private final String[] segments;
  
      public Key(String... segments) {
        this.segments = segments;
      }
  
      @Override
      public boolean equals(Object o) {
        if (!(o instanceof Key)) {
          return false;
        }
        Key that = (Key) o;
  
        return Arrays.equals(this.segments, that.segments);
      }
  
      @Override
      public int hashCode() {
        return Arrays.hashCode(segments);
      }
    }
  }
  