maven-javadoc-plugin/stale-data-encoding.patch

--- a/src/main/java/org/apache/maven/plugins/javadoc/StaleHelper.java
+++ b/src/main/java/org/apache/maven/plugins/javadoc/StaleHelper.java
@@ -40,6 +40,19 @@ import org.codehaus.plexus.util.cli.Commandline;
  */
 public class StaleHelper {
 
+    private static Charset getDataCharset()
+    {
+        if ( JavaVersion.JAVA_SPECIFICATION_VERSION.isAtLeast( "9" )
+            && JavaVersion.JAVA_SPECIFICATION_VERSION.isBefore( "12" ) )
+        {
+            return StandardCharsets.UTF_8;
+        }
+        else
+        {
+            return Charset.defaultCharset();
+        }
+    }
+
     /**
      * Compute the data used to detect a stale javadoc
      *
@@ -55,13 +68,7 @@ public class StaleHelper {
             String[] args = cmd.getArguments();
             Collections.addAll(options, args);
 
-            final Charset cs;
-            if (JavaVersion.JAVA_SPECIFICATION_VERSION.isAtLeast("9")
-                    && JavaVersion.JAVA_SPECIFICATION_VERSION.isBefore("12")) {
-                cs = StandardCharsets.UTF_8;
-            } else {
-                cs = Charset.defaultCharset();
-            }
+            final Charset cs = getDataCharset();
 
             for (String arg : args) {
                 if (arg.startsWith("@")) {
@@ -115,9 +122,11 @@ public class StaleHelper {
      */
     public static void writeStaleData(Commandline cmd, Path path) throws MavenReportException {
         try {
+            final Charset cs = getDataCharset();
+
             List<String> curdata = getStaleData(cmd);
             Files.createDirectories(path.getParent());
-            Files.write(path, curdata, StandardCharsets.UTF_8);
+            Files.write(path, curdata, cs);
         } catch (IOException e) {
             throw new MavenReportException("Error checking stale data", e);
         }