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import java.util.Objects;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.traversal.DocumentTraversal;
import org.w3c.dom.traversal.NodeFilter;
import org.w3c.dom.traversal.TreeWalker;

public class XmlWalker {

  private static final String regex = "\\d*[\\.\\,]\\d*";

  public static void main(String[] argv) throws Exception {
    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    DocumentBuilder loader = factory.newDocumentBuilder();
    Document document = loader.parse("sample.xml");

    DocumentTraversal traversal = (DocumentTraversal) document;

    TreeWalker walker =
        traversal.createTreeWalker(
            document.getDocumentElement(), NodeFilter.SHOW_ELEMENT, null, true);

    normalizeNumericNodes(walker);
  }

  private static final void normalizeNumericNodes(TreeWalker walker) {
    Node parent = walker.getCurrentNode();

    for (Node n = walker.firstChild(); n != null; n = walker.nextSibling()) {
      String text = n.getTextContent();
      if (Objects.nonNull(text) && text.matches(regex)) {
        n.setTextContent(text.replaceAll(",", "."));
      }
      normalizeNumericNodes(walker);
    }
    walker.setCurrentNode(parent);
  }
}