////////////////////////////////////////////////////////////////////////////////

 // checkstyle: Checks Java source code for adherence to a set of rules.

 // Copyright (C) 2001-2014  Oliver Burn

 //

 // This library is free software; you can redistribute it and/or

 // modify it under the terms of the GNU Lesser General Public

 // License as published by the Free Software Foundation; either

 // version 2.1 of the License, or (at your option) any later version.

 //

 // This library 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

 // Lesser General Public License for more details.

 //

 // You should have received a copy of the GNU Lesser General Public

 // License along with this library; if not, write to the Free Software

 // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 ////////////////////////////////////////////////////////////////////////////////

 package com.puppycrawl.tools.checkstyle;

 import java.util.Properties;

 /**

  * Resolves external properties from an

  * underlying <code>Properties</code> object.

  *

  * @author lkuehne

  */

 public final class PropertiesExpander

     implements PropertyResolver

 {

     /** the underlying Properties object. */

     private final Properties mProperties;

     /**

      * Creates a new PropertiesExpander.

      * @param aProperties the underlying properties to use for

      * property resolution.

      * @throws IllegalArgumentException indicates null was passed

      */

     public PropertiesExpander(Properties aProperties)

     {

         if (aProperties == null) {

             throw new IllegalArgumentException("cannot pass null");

         }

         mProperties = aProperties;

     }

     /** {@inheritDoc} */

     public String resolve(String aPropertyName)

     {

         return mProperties.getProperty(aPropertyName);

     }

 }