fix: correct the non-attached java-doc position in tree

gen.jdt/src/main/java/com/github/gumtreediff/gen/jdt/JdtWithCommentsVisitor.java

@@ -57,14 +57,29 @@ public boolean visit(Javadoc node) {
             if (node.getParent() == null)
                 //Then it is Javadoc attached to any program element,
                 //So we do as the same as the other Javadocs in the original visitors
-                node.accept(JdtWithCommentsVisitor.this);
+                return visitComment(node);
             return true;
         }
 
         public boolean visitComment(Comment node) {
             int start = node.getStartPosition();
             int end = start + node.getLength();
             Tree parent = findMostInnerEnclosingParent(context.getRoot(), start, end);
+            if (node.getParent() == null) {
+                //The attached ones have been already visited, and we do not want to add them twice.
+                //Then it is Javadoc attached to any program element,
+                //So we do as the same as the other Javadocs in the original visitors
+                trees.push(parent);
+                node.accept(JdtWithCommentsVisitor.this);
+
+                //fix the order in among the children
+                Tree wrongOrderChild = parent.getChild(parent.getChildren().size() - 1);
+                parent.getChildren().remove(wrongOrderChild);
+                insertChildProperly(parent, wrongOrderChild);
+
+                trees.pop();
+                return true;
+            }
             Tree t = context.createTree(nodeAsSymbol(node), new String(scanner.getSource(), start, end - start));
             t.setPos(start);
             t.setLength(node.getLength());