The TCP/IP connection to the host localhost, port 1433 has failed. Error: "Connection refused: connect

I want to connect Java class file with SQL server 2008. I have logged in with SQL server authentication use: sa, pass:123456. But i am receiving error in connectivity.

static String driver = "com.microsoft.sqlserver.jdbc.SQLServerDriver";
static String dburl = "jdbc:sqlserver://localhost\SQL2008:1433;Database=Java";
static String user = "sa";
static String password = "123456";


public static void update() throws Exception{
    String sql = "UPDATE Categories SET Id='COM' WHERE Id='LAP'";

    Class.forName(driver);
    Connection conn = DriverManager.getConnection(dburl, user, password);
    Statement stmt = conn.createStatement();
    stmt.executeUpdate(sql);
    conn.close();
}



public static void main(String[] args) throws Exception {
    Basic.update();
}


  Exception in thread "main" com.microsoft.sqlserver.jdbc.SQLServerException: The TCP/IP connection to the host localhost, port 1433 has failed. Error: "Connection refused: connect. 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:1048)
at com.microsoft.sqlserver.jdbc.SQLServerConnection.login(SQLServerConnection.java:829)
at com.microsoft.sqlserver.jdbc.SQLServerConnection.connect(SQLServerConnection.java:712)
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 Tutorials.jdbc.Basic.update(Basic.java:48)
at Tutorials.jdbc.Basic.main(Basic.java:72)