Connect to the MySql database using java in Singleton mode

Package com. adrop. util;
Import java. SQL .*;
Public class DBManager {
// User name
Private String user = "";
// Password
Private String password = "";
// Host
Private String host = "";
// Database name
Private String database = "";
// Private DBManager dbm = null;
/*
Private String url = "jdbc: mysql: //" + host + "/" + "useUnicode = true & characterEncoding = GB2312 ";
*/
Private String url = "";
Private Connection con = null;
Statement stmt;
/**
* Private constructor ensures that external entities cannot be instantiated and can only be provided by DBManager itself
* You can only have one instance.
* The connection is obtained based on the host, database name, database user name, and database user password.
* @ Param host String
* @ Param database String
* @ Param user String
* @ Param password String
*/
Private DBManager (String host, String database, String user, String password ){
This. host = host;
This. database = database;
This. user = user;
This. password = password;
// Display Chinese characters
This. url = "jdbc: mysql: //" + host + "/" + database +
"? UseUnicode = true & characterEncoding = GB2312 ";
Try {
Class. forName ("org. gjt. mm. mysql. Driver ");
}
Catch (ClassNotFoundException e ){
System. err. println ("class not found:" + e. getMessage ());
}
Try {
Con = DriverManager. getConnection (this. url, this. user, this. password );
// The connection type is ResultSet. TYPE_SCROLL_INSENSITIVE and ResultSet. CONCUR_READ_ONLY.
Stmt = con. createStatement (ResultSet. TYPE_SCROLL_INSENSITIVE,
ResultSet. CONCUR_READ_ONLY );
}
Catch (SQLException ){
System. err. println ("SQL exception:" + a. getMessage ());
}