大家帮我看看这是怎么回事？？
在做Struts2 OptionTransferSelect标签使用练习时，想实现一个“双向选择器”，并找到了一段这样的代码：
1. Action层
TransferSelect.java 

package com.mobilesoft.esales.webapp.action; 

import java.util.ArrayList; 

import java.util.Iterator; 

import java.util.List; 

import java.util.Map; 

import java.util.Set; 

import org.apache.log4j.Logger; 

public class TransferSelect extends BaseAction { 

private static final Logger logger = Logger.getLogger(DoubleListAction.class); 

  String[] leftRoles; 

  String[] rightRoles; 

public String execute(){  

return SUCCESS; 

  } 

public String transferSelect(){ 

  ArrayList<Roles> leftList=new ArrayList<Roles> ();  

  Roles leftRoles1=new Roles(); 

  leftRoles1.setRoleId(1); 

  leftRoles1.setRoleName("角色1"); 

  Roles leftRoles2=new Roles(); 

  leftRoles2.setRoleId(2); 

  leftRoles2.setRoleName("角色2"); 

  Roles leftRoles3=new Roles(); 

  leftRoles3.setRoleId(3); 

  leftRoles3.setRoleName("角色3"); 

  Roles leftRoles4=new Roles(); 

  leftRoles4.setRoleId(4); 

  leftRoles4.setRoleName("角色4"); 

  leftList.add(leftRoles1); 

  leftList.add(leftRoles2); 

  leftList.add(leftRoles3); 

  leftList.add(leftRoles4); 

  ArrayList<Roles> rightList=new ArrayList();  

  Roles rightRoles1=new Roles(); 

  rightRoles1.setRoleId(1); 

  rightRoles1.setRoleName("角色5"); 

  Roles rightRoles2=new Roles(); 

  rightRoles2.setRoleId(2); 

  rightRoles2.setRoleName("角色6"); 

  Roles rightRoles3=new Roles(); 

  rightRoles3.setRoleId(3); 

  rightRoles3.setRoleName("角色7"); 

  Roles rightRoles4=new Roles(); 

  rightRoles4.setRoleId(4); 

  rightRoles4.setRoleName("角色8"); 

  rightList.add(rightRoles1); 

  rightList.add(rightRoles2); 

  rightList.add(rightRoles3); 

  rightList.add(rightRoles4);  

  getRequest().setAttribute("rightList", rightList); 

  getRequest().setAttribute("leftList", leftList); 

return SUCCESS; 

  } 

public String transferSelectPost(){ 

  Map map=getRequest().getParameterMap(); 

  Set set=map.entrySet(); 

  Iterator iterator=set.iterator(); 

while(iterator.hasNext()){ 

  Map.Entry mapEntry=(Map.Entry)iterator.next(); 

if(mapEntry.getValue() instanceof String[]){ 

  String[] selectValues=(String[])mapEntry.getValue(); 

for(int i=0;i<selectValues.length;i++){ 

logger.fatal("For map test，The key is: "+mapEntry.getKey()+",value is :"+selectValues[i]);  

  } 

  }