content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF 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.apache.auron.util;
  
  import javax.annotation.Nullable;
  
  /**
   * A collection of static utility methods to validate input.
   *
   * <p>This class is modelled after Google Guava's Preconditions class, and partly takes code from
   * that class. We add this code to the Auron code base in order to reduce external dependencies.
   */
  public class Preconditions {
  
      // ------------------------------------------------------------------------
      //  Null checks
      // ------------------------------------------------------------------------
  
      /**
       * Ensures that the given object reference is not null. Upon violation, a {@code
       * NullPointerException} with no message is thrown.
       *
       * @param reference The object reference
       * @return The object reference itself (generically typed).
       * @throws NullPointerException Thrown, if the passed reference was null.
       */
      public static <T> T checkNotNull(@Nullable T reference) {
          if (reference == null) {
              throw new NullPointerException();
          }
          return reference;
      }
  
      /**
       * Ensures that the given object reference is not null. Upon violation, a {@code
       * NullPointerException} with the given message is thrown.
       *
       * @param reference The object reference
       * @param errorMessage The message for the {@code NullPointerException} that is thrown if the
       *     check fails.
       * @return The object reference itself (generically typed).
       * @throws NullPointerException Thrown, if the passed reference was null.
       */
      public static <T> T checkNotNull(@Nullable T reference, @Nullable String errorMessage) {
          if (reference == null) {
              throw new NullPointerException(String.valueOf(errorMessage));
          }
          return reference;
      }
  }
  