Database Connection was closed - but the connection is not null

Question

I have a class which connect to a MSSQL Database. The connection is successfully because if i run the code in my debugger (Eclipse) i can see that the connection is not null. Also the If-Statement is called because the connection is not null

protected void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {

String query = "My Query";

con = DBVerbindung();

//The connection is not null
if (con != null) {

try {

 //Here the connection is closed
 stmt = con.prepareStatement(query);

} catch (Exception e) {
                e.printStackTrace();

 } 
}




 private Connection DBVerbindung() {
 return DatabaseConnection.Verbindung();

 }

}

But in the next line if i want to call the preparedStatement i got a Connection fail error:

Here is my DatabaseConnection Class

   public class DatabaseConnection {

public static Connection Verbindung() {



     final String connectionUrlMsSQLDEV = "jdbc:sqlserver://XXXXX:1234;databaseName=hrpap_itha_apps_dev;user=HRPAP-dev;password=XXXXX";

    try {
    Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");



    } catch (ClassNotFoundException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    }
    try (Connection conn = DriverManager.getConnection(connectionUrlMsSQLDEV)) {

        if (conn != null) {
            System.out.println("Verbunden!");
        } else {
            System.out.println("Fehler: Verbindung konnte nicht hergestellt werden! ---> " + DatabaseConnection.class.getName() );
        }
        return conn;
    } catch (SQLException e) {
        System.err.format("SQL State: %s\n%s", e.getSQLState(), e.getMessage());
    } catch (Exception e) {
        e.printStackTrace();
    }
    return null;

}

}

So why is the connection at this point null ?

Thanks