content: package com.coveros.training.library.domainobjects;
  
  /**
   * These are the possible results of business functions
   * related to the library.  For example, you might
   * get ALREADY_REGISTERED_BOOK if you are trying to register
   * a book and it's already in the library.
   */
  public enum LibraryActionResults {
  
      ALREADY_REGISTERED_BOOK,
  
      /**
       * if a book isn't registered, then of course we cannot delete it.
       */
      NON_REGISTERED_BOOK_CANNOT_BE_DELETED,
  
      /**
       * if a borrower isn't registered, then of course we cannot delete it.
       */
      NON_REGISTERED_BORROWER_CANNOT_BE_DELETED,
      ALREADY_REGISTERED_BORROWER,
      BOOK_NOT_REGISTERED,
      BORROWER_NOT_REGISTERED,
      /**
       * someone already has this book checked out.
       */
      BOOK_CHECKED_OUT,
      SUCCESS,
      /**
       * if a method needs a book and none is provided
       */
      NO_BOOK_TITLE_PROVIDED,
      /**
       * if a method needs a borrower and none is provided
       */
      NO_BORROWER_PROVIDED,
      /**
       * may be used when initializing a variable of this type
       */
      NULL
  }
  