I always used ResourcedBundle to read *.properties like that:
ResourceBundle.getBundle("filename");
to get properties from "filename.properties".
the javadoc of ResourceBundle mentions "...PropertyResourceBundle uses a properties file to manage its resources...." so also have a look at the javadoc of PropertyResourceBundle.
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The biggest difference between a plain old Properties file and a ResourceBundle is that you can more easily deal with different Locales (so have different language) with ResourceBundles.
Take a look at the Internationalization tutorial found here http://java.sun.com/docs/books/tutorial/i18n/index.html