'--' must never appear in the text used to create the comment : Comment « XML « Java Tutorial

1. Java Tutorial
2. XML
3. Comment

import java.io.File;

import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.Comment;
import org.w3c.dom.Document;

public class Main {
  public static void main(String[] argv) throws Exception {

    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    factory.setValidating(true);

    factory.setExpandEntityReferences(false);

    Document doc = factory.newDocumentBuilder().parse(new File("filename"));
    Comment comment = doc.createComment("invalid -- comment");
    boolean validComment = comment.getNodeValue().indexOf("--") < 0;
  }
}