code: /*
   * 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.commons.lang;
  
  /**
   * <p>Thrown when an object is an instance of an unexpected type (a class or interface).
   * This exception supplements the standard <code>IllegalArgumentException</code>
   * by providing a more semantically rich description of the problem.</p>
   * 
   * <p><code>IllegalClassException</code> represents the case where a method takes
   * in a genericly typed parameter like Object (typically because it has to due to some
   * other interface it implements), but this implementation only actually accepts a specific
   * type, for example String. This exception would be used in place of
   * <code>IllegalArgumentException</code>, yet it still extends it.</p>
   * 
   * <pre>
   * public void foo(Object obj) {
   *   if (obj instanceof String == false) {
   *     throw new IllegalClassException(String.class, obj);
   *   }
   *   // do something with the string
   * }
   * </pre>
   * 
   * @author Matthew Hawthorne
   * @author Gary Gregory
   * @author Stephen Colebourne
   * @since 2.0
   * @version $Id: IllegalClassException.java 437554 2006-08-28 06:21:41Z bayard $
   */
  public class IllegalClassException extends IllegalArgumentException {
  
      /**
       * Required for serialization support.
       * 
       * @see java.io.Serializable
       */
      private static final long serialVersionUID = 8063272569377254819L;
  
      /**
       * <p>Instantiates with the expected type, and actual object.</p>
       * 
       * @param expected  the expected type
       * @param actual  the actual object
       * @since 2.1
       */
      public IllegalClassException(Class expected, Object actual) {
          super(
              "Expected: "
                  + safeGetClassName(expected)
                  + ", actual: "
                  + (actual == null ? "null" : actual.getClass().getName()));
      }
  
      /**
       * <p>Instantiates with the expected and actual types.</p>
       * 
       * @param expected  the expected type
       * @param actual  the actual type
       */
      public IllegalClassException(Class expected, Class actual) {
          super(
              "Expected: "
                  + safeGetClassName(expected)
                  + ", actual: "
                  + safeGetClassName(actual));
      }
  
      /**
       * <p>Instantiates with the specified message.</p>
       * 
       * @param message  the exception message
       */
      public IllegalClassException(String message) {
          super(message);
      }
  
      /**
       * <p>Returns the class name or <code>null</code> if the class is
       * <code>null</code>.</p>
       * 
       * @param cls  a <code>Class</code>
       * @return the name of <code>cls</code>, or <code>null</code> if if <code>cls</code> is <code>null</code>.
       */
      private static final String safeGetClassName(Class cls) {
          return cls == null ? null : cls.getName();
      }
  
  }
  