JAVA连接Oracle的问题
这个是我下的一个代码   有一些看不懂   请教各位大哥

ClassPath=.;E:\j2sdk14\lib\tools.jar;E:\oracle\ora90\jdbc\lib\classes12.zip


测试的电脑已经装好Oracle客户端，而且用SQLplus可以连接上。
/*
*   This   sample   shows   how   to   list   all   the   names   from   the   EMP   table
*
*   It   uses   the   JDBC   THIN   driver.     See   the   same   program   in   the
*   oci8   samples   directory   to   see   how   to   use   the   other   drivers.
*/

//   You   need   to   import   the   java.sql   package   to   use   JDBC
import   java.sql.*;

class   Test
{
    public   static   void   main   (String   args   [])
              throws   SQLException
    {
        //   Load   the   Oracle   JDBC   driver
        DriverManager.registerDriver(new   oracle.jdbc.OracleDriver());
/*   try{
    Class.forName( "oracle.jdbc.driver.OracleDriver ");
}catch(Exception   e){
    System.out.println( "No   Driver! ");
}
*/  
        //   Connect   to   the   database
        //   You   must   put   a   database   name   after   the   @   sign   in   the   connection   URL.
        //   You   can   use   either   the   fully   specified   SQL*net   syntax   or   a   short   cut
        //   syntax   as   <host> : <port> : <sid> .     The   example   uses   the   short   cut   syntax.
        String   url   =   "jdbc:oracle:thin:@172.28.31.85:1521:YIKATONG ";
        String   userName   =   "scott ";
        String   password   =   "tiger ";

        if   (args.length   >   0)   url   =   args[0];
        if   (args.length   >   1)   userName   =   args[1];
        if   (args.length   >   2)   password   =   args[2];
System.out.println(url);
System.out.println(userName);
System.out.println(password);
        Connection   conn   =
            DriverManager.getConnection   (url,   userName,   password);

        //   Create   a   Statement
        Statement   stmt   =   conn.createStatement   ();

      //   Select   the   ENAME   column   from   the   EMP   table
        ResultSet   rset   =   stmt.executeQuery   ( "select   *   from   Test ");

        //   Iterate   throu