content: /*
   * Universal Password Manager
   * Copyright (C) 2005-2013 Adrian Smith
   *
   * This file is part of Universal Password Manager.
   *   
   * Universal Password Manager is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * Universal Password Manager is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with Universal Password Manager; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
   */
  package com._17od.upm.util;
  
  /**
   * Validator is inspired by Google Guava as linked below and is used in lieu of
   * adding the full Google Guava library package to this project.
   * 
   * https://code.google.com/p/guava-libraries/wiki/PreconditionsExplained
   * 
   * This class helps to add precondition argument checks to public methods to
   * avoid Null as much as possible as also inspired by Google Guava here:
   * 
   * https://code.google.com/p/guava-libraries/wiki/UsingAndAvoidingNullExplained
   * 
   * @author markyv
   * @version 0.0.4
   */
  public class Validator {
  
      private Validator() {
          throw new AssertionError("Cannot instantiate this class");
      }
      
      /**
       * Validates that an expression is true and throws an error if it false.
       * This is meant to be used in validating arguments for public methods.
       * 
       * @param expression The expression to evaluate as true, an assertion
       * @param errorMessage The error message to provide for the thrown exception
       * @throws IllegalArgumentException 
       *         with the provided errorMessage if expression is false
       */
      public static void checkArgument(boolean expression, String errorMessage) {
          if (!expression) {
              throw new IllegalArgumentException(errorMessage.toString());
          }
      }
  
      /**
       * Convenience method to validate an argument is not null. Rather than throw
       * a NullPointerError, throw an
       * 
       * @param toCheck The object to confirm is not null
       * @param errorMessage The error message to provide for the thrown exception
       * @return toCheck as a convenience for assignment
       * @throws IllegalArgumentException
       *             to make it clear that there is a problem with the argument
       *             being supplied to the method rather than a bug in the method
       *             itself.
       * @see Validator#checkArgument(boolean, String)
       */
      public static void checkNotNull(Object toCheck, String errorMessage) {
          checkArgument(null != toCheck, errorMessage);
          // After upgrade to >JRE 1.4, use generics to return the object
      }
  }
  