用1个月重构了同事写的烂代码，我总结出了15条重写烂代码的经验！

remoteBatchQuery(param);

for(int i=0;i<n;i++){
  remoteSingleQuery(param)
}

public void getUserInfo（String name,String age,String sex,String mobile,String idNo){
  // do something ...
}

public void getUserInfo（UserInfoParamDTO userInfoParamDTO){
  // do something ...
}
class UserInfoParamDTO{
  private String name;
  private String age; 
  private String sex;
  private String mobile;
  private String idNo;
}

// 商户A处理句柄
CompanyAHandler implements RequestHandler {
   Resp hander(req){
   //查询商户信息
   queryMerchantInfo();
   //加签
   signature();
   //http请求（A商户假设走的是代理）
   httpRequestbyProxy()
   //验签
   verify();
   }
}
// 商户B处理句柄
CompanyBHandler implements RequestHandler {
   Resp hander(Rreq){
   //查询商户信息
   queryMerchantInfo();
   //加签
   signature();
   // http请求（B商户不走代理，直连）
   httpRequestbyDirect();
   // 验签
   verify(); 
   }
}

abstract class AbstractMerchantService  { 
     //模板方法流程
     Resp handlerTempPlate(req){
           //查询商户信息
           queryMerchantInfo();
           //加签
           signature();
           //http 请求
           httpRequest();
           // 验签
           verifySinature();
     }
      // Http是否走代理（提供给子类实现）
      abstract boolean isRequestByProxy();
}

    public void test(UserStatus userStatus){
        if (userStatus != UserStatus.BANNED && userStatus != UserStatus.DELETED && userStatus != UserStatus.FROZEN) {
            //doSomeThing
            return
        }
    }

    public void test(UserStatus userStatus){
        if (isUserActive(userStatus)) {
            //doSomeThing
        }
    }
    private boolean isUserActive(UserStatus userStatus) {
        return userStatus != UserStatus.BANNED && userStatus != UserStatus.DELETED && userStatus != UserStatus.FROZEN;
    }

if (list == null || list.size() == 0) {
  return null;
}

if (CollectionUtils.isEmpty(list)) {
   return null;
}

public class Test {
    private String name;
    private Vector<Order> orders = new Vector<Order>();
    public void printOwing() {
        //print banner
        System.out.println("****************");
        System.out.println("*****customer Owes *****");
        System.out.println("****************");
        //calculate totalAmount
        Enumeration env = orders.elements();
        double totalAmount = 0.0;
        while (env.hasMoreElements()) {
            Order order = (Order) env.nextElement();
            totalAmount += order.getAmout();
        }
        //print details
        System.out.println("name:" + name);
        System.out.println("amount:" + totalAmount);
        ......
    }
}

public class Test {
    private String name;
    private Vector<Order> orders = new Vector<Order>();
    public void printOwing() {
        //print banner
        printBanner();
        //calculate totalAmount
        double totalAmount = getTotalAmount();
        //print details
        printDetail(totalAmount);
    }
    void printBanner(){
        System.out.println("****************");
        System.out.println("*****customer Owes *****");
        System.out.println("****************");
    }
    double getTotalAmount(){
        Enumeration env = orders.elements();
        double totalAmount = 0.0;
        while (env.hasMoreElements()) {
            Order order = (Order) env.nextElement();
            totalAmount += order.getAmout();
        }
        return totalAmount;
    }
    void printDetail(double totalAmount){
        System.out.println("name:" + name);
        System.out.println("amount:" + totalAmount);
    }   
}

FileInputStream fdIn = null;
try {
    fdIn = new FileInputStream(new File("/捡田螺的小男孩.txt"));
} catch (FileNotFoundException e) {
    log.error(e);
} catch (IOException e) {
    log.error(e);
}finally {
    try {
        if (fdIn != null) {
            fdIn.close();
        }
    } catch (IOException e) {
        log.error(e);
    }
}

public void transfer(TransferDTO transferDTO){
    log.info("invoke tranfer begin");
    //打印入参
    log.info("invoke tranfer,paramters:{}",transferDTO);
    try {
      res=  transferService.transfer(transferDTO);
    }catch(Exception e){
     log.error("transfer fail,account：{}",
     transferDTO.getAccount（）)
     log.error("transfer fail,exception:{}",e);
    }
    log.info("invoke tranfer end");
    }

//老接口
void oldService(A,B){
  //兼容新接口，传个null代替C
  newService(A,B,null);
}
//新接口，暂时不能删掉老接口，需要做兼容。
void newService(A,B,C){
  ...
}

String name = list.get(1).getName(); //list可能越界，因为不一定有2个元素哈

if(CollectionsUtil.isNotEmpty(list)&& list.size()>1){
        String name = list.get(1).getName();
        }