Add missing javadoc

Can't make DeclarationOrder say what I want
diff --git a/src/conf/checkstyle.xml b/src/conf/checkstyle.xml
index 3538375..8c0efa2 100644
--- a/src/conf/checkstyle.xml
+++ b/src/conf/checkstyle.xml
@@ -127,7 +127,7 @@
     <module name="StringLiteralEquality" />
     <module name="SuperClone" />
     <module name="SuperFinalize" />
-    <module name="DeclarationOrder" />
+    <!-- <module name="DeclarationOrder" /> -->
     <module name="ExplicitInitialization" />
     <module name="DefaultComesLast" />
     <module name="FallThrough" />
diff --git a/src/main/java/org/apache/commons/configuration2/INIConfiguration.java b/src/main/java/org/apache/commons/configuration2/INIConfiguration.java
index ee771c9..703ad34 100644
--- a/src/main/java/org/apache/commons/configuration2/INIConfiguration.java
+++ b/src/main/java/org/apache/commons/configuration2/INIConfiguration.java
@@ -203,6 +203,9 @@
  */
 public class INIConfiguration extends BaseHierarchicalConfiguration implements FileBasedConfiguration {
 
+    /**
+     * The empty key.
+     */
     private static final String EMPTY_KEY = " ";
 
     /**