肯请高手帮我程序提优化，规范一下，谢谢

/*
这个类主要是连接数据库，暂是不用连接池
*/
package com.chainjee;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.util.ArrayList;
import java.util.Hashtable;
import java.util.Iterator;


public class MyDatabase {
private Connection conn=null;
private PreparedStatement comm=null;

public MyDatabase(){
connectDB();
}

public void connectDB(){
try{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
conn=DriverManager.getConnection("jdbc:odbc:test","sa","sa");
}catch(Exception ex){
System.out.println(ex.toString());
}
}

public void setPrepareSQL(String strSQL) throws Exception{
comm=conn.prepareStatement(strSQL);
}

public void setString(int cols,String defaultValue) throws Exception{
comm.setString(cols,defaultValue);
}

public void setInt(int cols,int defaultValue) throws Exception{
comm.setInt(cols,defaultValue);
}

public Connection getConnection(){
return this.conn;
}

public int executeUpdate(){
int recordAffected=0;
try{
recordAffected=comm.executeUpdate();
}catch(Exception ex){
}
return recordAffected;
}

/*以arrayList的形式返回数据库记录列表*/
public ArrayList executeQuery() {
ArrayList arrayList=new ArrayList();
ResultSet res1=null;
try{
res1=comm.executeQuery();
ResultSetMetaData rsm=res1.getMetaData();
while(res1.next()){
Hashtable hb=new Hashtable();
for(int i=1;i<=rsm.getColumnCount();i++){
String name=rsm.getColumnName(i);
Object value=res1.getObject(i);
hb.put(name,""+value);
}
arrayList.add(hb);
}
}catch(Exception ex){
return null;
}finally{
try{
res1.close();
}catch(Exception e){}
}
return arrayList;
}

/*System Test*/
public static void main(String[] args) throws Exception{
}
}