oracle和Mysql连接数据库

Mysql方式：
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class MysqlDB {
 private String strClass = "com.mysql.jdbc.Driver";
 private String strDriver = "jdbc:mysql://localhost:3306/s_smdb";
 private String strUser = "root";
    private String strPwd = "123";
 private Connection conn = null;
 private Statement stmt = null;
 private ResultSet rs = null;
 private static CDBAccess instance = null;
 
 private CDBAccess() throws ClassNotFoundException, SQLException{
  Class.forName(strClass);
  conn = DriverManager.getConnection(strDriver,strUser,strPwd) ;
 }
 
 public static CDBAccess getInstance() throws ClassNotFoundException, SQLException{
  if(instance == null){
   instance = new CDBAccess();
  }
  
  return instance;
 }
 
 public ResultSet executeQuery(String strsql) throws SQLException{
  stmt = conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_UPDATABLE);
  rs = stmt.executeQuery(strsql);
  
  return rs;
 }
 
 public int executeUpdate(String strsql) throws SQLException{
  int i = 0;
  stmt = conn.createStatement();
  i = stmt.executeUpdate(strsql);
  
  return i;
 }
 
 
 public void close() throws SQLException{
  if(rs != null){
   rs.close();
  }
  if(stmt != null){
   stmt.close();
  }
  if(conn != null){
   conn.close();
  }
  if(instance != null){
   instance = null;
  }
 }
}
Oracle方式：
package util;
import java.sql.Connection;
import java.sql.