Fix the Checkstyle DTD URL.
diff --git a/checkstyle-suppressions.xml b/checkstyle-suppressions.xml
index 448c654..0a54532 100644
--- a/checkstyle-suppressions.xml
+++ b/checkstyle-suppressions.xml
@@ -17,8 +17,8 @@
-->
<!DOCTYPE suppressions PUBLIC
- "-//Puppy Crawl//DTD Suppressions 1.1//EN"
- "http://www.puppycrawl.com/dtds/suppressions_1_1.dtd">
+ "-//Checkstyle//DTD SuppressionFilter Configuration 1.1//EN"
+ "https://checkstyle.org/dtds/suppressions_1_1.dtd">
<suppressions>
<!-- On Windows, it appears that Checkstyle matches files using \ delims -->
diff --git a/checkstyle.xml b/checkstyle.xml
index 987b86e..a8e9ff9 100644
--- a/checkstyle.xml
+++ b/checkstyle.xml
@@ -17,8 +17,8 @@
-->
<!DOCTYPE module PUBLIC
- "-//Puppy Crawl//DTD Check Configuration 1.1//EN"
- "http://www.puppycrawl.com/dtds/configuration_1_1.dtd">
+ "-//Checkstyle//DTD Checkstyle Configuration 1.1//EN"
+ "https://checkstyle.org/dtds/configuration_1_1.dtd">
<!-- Commons Net customization of default Checkstyle behavior -->
<module name="Checker">