checkstyle.xml

<?xml version="1.0"?>
<module name="Checker">
	<!-- ends with newline -->
	<module name="NewlineAtEndOfFile"/>

	<!-- tab indentation -->
	<module name="RegexpSinglelineJava">
		<property name="format" value="^\t* "/>
		<property name="message" value="Indent must use tab characters"/>
		<property name="ignoreComments" value="true"/>
	</module>
</module>