try { 
   Class.forName("com.mysql.jdbc.Driver"); 
} 
catch(ClassNotFoundException e) { 
   System.out.println("找不到驱动程序"); 
}

try { 
   String url = "jdbc:mysql://localhost:3306/GUESTBOOK?user=root&password=123456"; 
   Connection conn = DriverManager.getConnection(url); 
   if(!conn.isClosed()) 
   System.out.println("数据库连接成功!");
   conn.close(); 
} 
catch(SQLException e) { 
   .... 
}

String url = "jdbc:mysql://localhost:3306/AddressBook"; 
String user = "ZhuJun"; 
String password = "123456"; 
Connection conn = DriverManager.getConnection(url, user, password);

import java.sql.*;
public class TestJDBC {
 public static void main(String[] args) throws Exception {
   Class.forName("com.mysql.jdbc.Driver");
   String url = "jdbc:mysql://localhost:3306/2";
   String user = "root";
   String password = "19870714";
   Connection conn = DriverManager.getConnection(url, user, password);
   if(!conn.isClosed())
   {
   System.out.println("success");
   }
   conn.close();
 }
}