I am trying to connect to MSSQL 2008 server from Java

here is a program

import java.sql.*;

public class connectURL {

    public static void main(String[] args) {

        // Create a variable for the connection string.
        String connectionUrl = "jdbc:sqlserver://localhost/SQLEXPRESS/Databases/HelloWorld:1433;";// +
            //"databaseName=HelloWorld;integratedSecurity=true;";

        // Declare the JDBC objects.
        Connection con = null;
        Statement stmt = null;
        ResultSet rs = null;

            try {
                // Establish the connection.
                Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
                    con = DriverManager.getConnection(connectionUrl);

                    // Create and execute an SQL statement that returns some data.
                    String SQL = "SELECT TOP 10 * FROM Person.Contact";
                    stmt = con.createStatement();
                    rs = stmt.executeQuery(SQL);

                    // Iterate through the data in the result set and display it.
                    while (rs.next()) {
                        System.out.println(rs.getString(4) + " " + rs.getString(6));
                    }
            }

        // Handle any errors that may have occurred.
        catch (Exception e) {
            e.printStackTrace();
        }

        finally {
            if (rs != null) try { rs.close(); } catch(Exception e) {}
                if (stmt != null) try { stmt.close(); } catch(Exception e) {}
                if (con != null) try { con.close(); } catch(Exception e) {}
        }
    }
}

But it shows error as

com.microsoft.sqlserver.jdbc.SQLServerException: The TCP/IP connection to the host localhost/SQLEXPRESS/Databases/HelloWorld, port 1433 has failed. Error: "null. Verify the connection properties, check that an instance of SQL Server is running on the host and accepting TCP/IP connections at the port, and that no firewall is blocking TCP connections to the port.".
    at com.microsoft.sqlserver.jdbc.SQLServerException.makeFromDriverError(SQLServerException.java:170)
    at com.microsoft.sqlserver.jdbc.SQLServerConnection.connectHelper(SQLServerConnection.java:1049)
    at com.microsoft.sqlserver.jdbc.SQLServerConnection.login(SQLServerConnection.java:833)
    at com.microsoft.sqlserver.jdbc.SQLServerConnection.connect(SQLServerConnection.java:716)
    at com.microsoft.sqlserver.jdbc.SQLServerDriver.connect(SQLServerDriver.java:841)
    at java.sql.DriverManager.getConnection(Unknown Source)
    at java.sql.DriverManager.getConnection(Unknown Source)
    at connectURL.main(connectURL.java:43)

I have given followed all the instructions as given in http://teamtutorials.com/database-tutorials/configuring-and-creating-a-database-in-ms-sql-2008

What can be the problem ?