Singelton pattern

15 Dec 2003

      Dear my friends...

I tried this singelton pattern. But I got this error
message:
===
patrixlinux@patrix:~/arsip/My/coba-2x/1> javac
Connector.java
Connector.java:2: cannot resolve symbol
symbol  : class Connection
location: class Connector
       private static Connection conn;
                      ^
Connector.java:18: cannot resolve symbol
symbol  : class Connection
location: class Connector
       public static Connection getConnection() {
                     ^
Connector.java:7: cannot resolve symbol
symbol  : variable DriverManager
location: class Connector
       conn =
DriverManager.getConnection("jdbc:mysql://localhost/amt?user=root&password=pandawa5");
              ^
Connector.java:12: cannot resolve symbol
symbol  : class SQLException
location: class Connector
             } catch (SQLException sqle) {
                      ^
Connector.java:31: cannot resolve symbol
symbol  : class SQLException
location: class Connector
                   } catch (SQLException sqle) {
                            ^
Connector.java:41: cannot resolve symbol
symbol  : class PreparedStatement
location: class Menu
     PreparedStatement ps = null;
     ^
Connector.java:44: cannot resolve symbol
symbol  : class Connection
location: class Menu
       Connection con = Connector.getConnection();
       ^
Connector.java:47: cannot resolve symbol
symbol  : class SQLException
location: class Menu
     } catch (SQLException sqle) {
              ^
Connector.java:51: cannot resolve symbol
symbol  : class SQLException
location: class Menu
       } catch (SQLException sqle) {
                ^
9 errors
patrixlinux@patrix:~/arsip/My/coba-2x/1>
===

And here is my simple code:
===
public class Connector {
       private static Connection conn;

       private Connector() {
             try {

Class.forName("com.mysql.jdbc.Driver");
       conn =
DriverManager.getConnection("jdbc:mysql://localhost/amt?user=root&password=pandawa5");

       System.out.println("Connected");
             } catch (ClassNotFoundException cnfe) {
                   cnfe.printStackTrace();
             } catch (SQLException sqle) {
                   sqle.printStackTrace();
             }
       }

       // Connection akan di-inisial sekali saja.
       public static Connection getConnection() {
             if (conn == null) {
                   new Connector();
             }

             return conn;
       }

       public static void closeConnection() {
             if (conn != null) {
                   try {
                         conn.close();

System.out.println("Disconnected");
                   } catch (SQLException sqle) {
                         sqle.printStackTrace();
                   }
             }
       }
 }

 class Menu {
   //....
   public static void customer() {
     PreparedStatement ps = null;

     try {
       Connection con = Connector.getConnection();
       ps = con.prepareStatement("SELECT customerid
FROM customer");
       //.....
     } catch (SQLException sqle) {
     } finally {
       try {
         if (ps != null) ps.close();
       } catch (SQLException sqle) {
       }      
     }
   }
 }
===

Anybody would be so nice to teach me, please....

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Singelton pattern

Prabu Subroto