accountdatabasefactory.cs

模拟银行系统的实现

using System;
using System.Collections.Generic;
using System.Text;

namespace Project1
{
    public class AccountDatabaseFactory
    {
        private static AccountDatabase DB_INSTANCE = createInstance();

        /// <summary>
        /// Create an instance of the AccountDatabase
        /// </summary>
        /// <returns>An instance of the AccountDatabase</returns>
        private static AccountDatabase createInstance()
	    {
		    try
		    {
			    AccountDatabase accountDatabase = new AccountDatabaseImp();

			    return accountDatabase;
		    }
		    catch (Exception e)
		    {
			    Console.WriteLine(e.ToString());
                return null;
		    }
	    }

        /// <summary>
        /// Get an instance of account database
        /// </summary>
        /// <returns>an instance of AccountDatabase</returns>
	    public static AccountDatabase getDatabaseInstance()
	    {
	    	return DB_INSTANCE;
	    }
	    	    
	    /// <summary>
	    /// Make sure this class cannot be initialized
	    /// </summary>
	    private AccountDatabaseFactory()
	    {
		    // do nothing
	    }
    }
}