fix warnings

Author: rbri

src/main/java/org/htmlunit/cyberneko/xerces/dom/CharacterDataImpl.java

@@ -36,7 +36,7 @@ public abstract class CharacterDataImpl extends ChildNode {
     protected String data_;
 
     /** Empty child nodes. */
-    private static final NodeList singletonNodeList = new NodeList() {
+    private static final NodeList EMPTY_NODE_LIST_SINGLETON = new NodeList() {
         @Override
         public Node item(final int index) {
             return null;
@@ -64,7 +64,7 @@ protected CharacterDataImpl(final CoreDocumentImpl ownerDocument, final String d
      */
     @Override
     public NodeList getChildNodes() {
-        return singletonNodeList;
+        return EMPTY_NODE_LIST_SINGLETON;
     }
 
     /*

src/test/java/org/htmlunit/cyberneko/AbstractCanonicalTest.java

@@ -67,7 +67,6 @@ public abstract class AbstractCanonicalTest {
                         = new File("target/data/output");
 
     protected static Stream<Arguments> testFiles() {
-        // System.out.println(canonicalDir.getAbsolutePath());
         OUTOUT_DIR.mkdirs();
 
         final List<File> dataFiles = new ArrayList<>();

src/test/java/org/htmlunit/cyberneko/util/FastHashMapTest.java

@@ -289,8 +289,8 @@ public void growFromSmall_InfiniteLoopIsssue() {
      * Test serialization, should work out of the box, just to
      * ensure nobody removes that.
      *
-     * @throws IOException
-     * @throws ClassNotFoundException
+     * @throws IOException in case of error
+     * @throws ClassNotFoundException in case of error
      */
     @Test
     public void serializable() throws IOException, ClassNotFoundException {