XML : Error reported by XML parser:XML document structures must start and end within the same entity

i'm trying this example from here

it's a simple example i just try to execute a an xquery query on an xml document (books.xml).

I keep having this error that say that XML document structures must start and end within the same entity.

   run:   Error on line 33 column 8 of books.xml:   SXXP0003: Error reported by XML parser: XML document structures must start and end    within the same entity.    javax.xml.xquery.XQException: org.xml.sax.SAXParseException; systemId:    file:/C:/Users/Ahmed/Documents/NetBeansProjects/JavaXquery/books.xml; lineNumber:   33; columnNumber: 8; XML document structures must start and end within the same   entity.  at com.saxonica.xqj.SaxonXQPreparedExpression.executeQuery(SaxonXQPreparedExpression.java:101)  at javaxquery.Main.execute(Main.java:40)  at javaxquery.Main.main(Main.java:21)  Caused by: net.sf.saxon.trans.XPathException: org.xml.sax.SAXParseException;      systemId: file:/C:/Users/Ahmed/Documents/NetBeansProjects/JavaXquery/books.xml;     lineNumber: 33; columnNumber: 8; XML document structures must start and end within the same entity..    

i check over and over my xml file and it's valid

this the xml file books.xml

  <?xml version="1.0" encoding="UTF-8"?>  <books>    <book category="JAVA">      <title lang="en">Learn Java in 24 Hours</title>      <author>Robert</author>      <year>2005</year>      <price>30.00</price>  </book>    <book category="DOTNET">      <title lang="en">Learn .Net in 24 hours</title>      <author>Peter</author>      <year>2011</year>      <price>70.50</price>  </book>    <book category="XML">      <title lang="en">Learn XQuery in 24 hours</title>      <author>Robert</author>      <author>Peter</author>      <year>2013</year>      <price>50.00</price>  </book>    <book category="XML">      <title lang="en">Learn XPath in 24 hours</title>      <author>Jay Ban</author>      <year>2010</year>      <price>16.50</price>  </book>    </books>    

And this is my code java

  package javaxquery;      import java.io.FileNotFoundException;      import javax.xml.xquery.XQConnection;  import javax.xml.xquery.XQDataSource;  import javax.xml.xquery.XQException;  import javax.xml.xquery.XQPreparedExpression;  import javax.xml.xquery.XQResultSequence;    import com.saxonica.xqj.SaxonXQDataSource;    public class Main {    public static void main(String[] args){    try {       execute();    }      catch (FileNotFoundException e) {       e.printStackTrace();    }      catch (XQException e) {       e.printStackTrace();    }   }  private static void execute() throws FileNotFoundException, XQException{    XQDataSource ds = new SaxonXQDataSource();    XQConnection conn = ds.getConnection();   String s = "for $x in doc(\"books.xml\")/books/book where $x/price>30 return $x/title" ;    XQPreparedExpression exp = conn.prepareExpression(s) ;    XQResultSequence result = exp.executeQuery();         while (result.next()) {       System.out.println(result.getItemAsString(null));    }     }    }