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.lang.reflect.Constructor;
  import java.lang.reflect.Method;
  import java.lang.reflect.Modifier;
  
  class ClassCreation {
  
    private ClassCreation() {
      // Utility class
    }
  
    static <X> X callCreateMethod(String clazz, Class<X> typeOfClass, Config configToUse)
        throws ReflectiveOperationException {
  
      // Use the context class loader since this is what the `--ext`
      // flag modifies.
      Class<?> classClazz =
          Class.forName(clazz, true, Thread.currentThread().getContextClassLoader());
  
      try {
        Method create = classClazz.getMethod("create", org.openqa.selenium.grid.config.Config.class);
  
        if (!Modifier.isStatic(create.getModifiers())) {
          throw new IllegalArgumentException(
              String.format("Class %s's `create(Config)` method must be static", clazz));
        }
  
        if (!typeOfClass.isAssignableFrom(create.getReturnType())) {
          throw new IllegalArgumentException(
              String.format("Class %s's `create(Config)` method must be static", clazz));
        }
  
        return typeOfClass.cast(create.invoke(null, configToUse));
      } catch (NoSuchMethodException e) {
        // Check to see if there's a public no-arg constructor
        Constructor<? extends X> constructor;
        try {
          constructor = classClazz.asSubclass(typeOfClass).getConstructor();
        } catch (NoSuchMethodException e2) {
          throw new IllegalArgumentException(
              String.format(
                  "Class %s must have a static `create(Config)` method or a default constructor",
                  clazz));
        }
        return constructor.newInstance();
      }
    }
  }
  