Error using API JAVA

I am trying run the following Query using the API Java for Quip and gave to error in the method “executeQuery”.

error Message:
java.lang.NullPointerException.

Code :
import java.util.;
import com.softwareag.xtools.quip.xqueryAPI.
;

public class testeQuip {
public static void main(String [] args){
Properties obj = new Properties();
StringBuffer stringbuffer1 = new StringBuffer();


try {
stringbuffer1.append( “c:/Quip/examples/data/” );
//stringbuffer1.append( “file://.” );

obj.put(“home”,“c:/Quip/examples/” );
obj.put(“quipcmd”,“c:/Quip/quip.exe” );

Connection Conexao = DriverManager.getConnection( stringbuffer1.toString(), (Properties)obj );
QueryResult Resultado =
Conexao.executeQuery(“let $b := document(“xmp-data.xml”)/bib/book return { $b/title }”);
System.out.println(Resultado.getRawString());
}
catch (XQueryException XQEx) {
System.out.println("XQueryException: " + XQEx.getMessage());
}
}
}