Fix checkstyle

Author: CalvinKirs

NOTICE.txt

@@ -4,7 +4,7 @@ Copyright 2016-2025 The Apache Software Foundation
 This product includes software developed at
 The Apache Software Foundation (http://www.apache.org/).
 
-This product contains code form the Netty Project:
+This product contains code from the Netty Project:
 ---------------------------------------------------
 The Netty Project
 =================

dev/checkstyle/suppressions.xml

@@ -37,7 +37,7 @@
   <suppress checks="Header" files="AutoCloseables.java|Collections2.java" />
 
   <!-- no license file in vendored dependencies -->
-  <suppress checks="Header" files="IntObjectMap.java|IntObjectHashMap.java" />
+  <suppress checks="Header" files="IntObjectMap.java|IntObjectHashMap.java|Preconditions.java" />
 
   <!-- Suppress certain checks requiring many code changes, that add little benefit -->
   <suppress checks="NoFinalizer|OverloadMethodsDeclarationOrder|VariableDeclarationUsageDistance" files=".*" />

pom.xml

@@ -739,6 +739,11 @@ under the License.
               <file>${maven.multiModuleProjectDirectory}/dev/license/asf-java.license</file>
               <delimiter>package</delimiter>
             </licenseHeader>
+            <excludes>
+              <exclude>**/Preconditions.java</exclude>
+              <exclude>**/IntObjectMap.java</exclude>
+              <exclude>**/IntObjectHashMap.java</exclude>
+            </excludes>
           </java>
         </configuration>
         <executions>