checkstyle: Utility classes should not have a public or default constructor

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/fileupload/trunk@1456837 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/src/main/java/org/apache/commons/fileupload/util/mime/QuotedPrintableDecoder.java b/src/main/java/org/apache/commons/fileupload/util/mime/QuotedPrintableDecoder.java
index 40399be..cc5e6d0 100644
--- a/src/main/java/org/apache/commons/fileupload/util/mime/QuotedPrintableDecoder.java
+++ b/src/main/java/org/apache/commons/fileupload/util/mime/QuotedPrintableDecoder.java
@@ -46,6 +46,13 @@
     }
 
     /**
+     * Hidden constructor, this class must not be instantiated.
+     */
+    private QuotedPrintableDecoder() {
+        // do nothing
+    }
+
+    /**
      * decode the uuencoded byte data writing it to the given output stream
      *
      * @param data   The array of byte data to decode.