如何写酷的代码.ppt

,目录,IF/SWITCH语句 复杂的、嵌套的IF/SWITCH语句,循环语句. 多层嵌套的循环语句，经常跟IF语句一起使用,A,B,圈复杂度 从理论上分析这两种坏味道,C,解决之道. 如何解决？值得探讨的课题,D,2,代码的坏味道带来的问题,破窗效应,代码的坏味道带来的问题,破窗效应,代码的坏味道带来的问题,破窗效应,代码的坏味道带来的问题,破窗效应,代码的坏味道带来的问题,冰山一角,代码的坏味道带来的问题,软件成本 Costtotal = costdevelop + costmaintain Costmaintain = Costunderstand + costchange + costtest+costdeploy Costmaintain costdevelop,代码的坏味道之IF语句,1.判断集合不为空,if (employeePositionList != null ,2.判断对象不为空,if (empSalarySet.getEffictiveDate()!= null if (empSalarySet.getInvalDate()!=null & empSalarySet.getInvalDate()!=“) .,代码的坏味道之IF语句,3.判断不为空 byte bufKey = RedisCacheInterceptor. stringSerializer.serialize(session.getId(); byte bufValue = connection.get(bufKey); if (bufValue != null) try return RedisCacheInterceptor. javaSerializer.deserializeInto(bufValue, session); catch (IOException e) e.printStackTrace(); catch (ClassNotFoundException e) e.printStackTrace(); return null;,代码的坏味道之IF语句,3.判断不为空 if (orgId != null) List employeePositionList =orgDataService .getEmployeePositionByOrgId(getTenantId(), orgId); Map empMap = new HashMap(); List empList = new ArrayList(); if (employeePositionList != null ,代码的坏味道之IF语句,4.判断为空 public ResponseBody SalarySetPage getList(Integer currentPageNo, Integer pageSize, Long orgId) (“EmpTreatmentController.getList()“); if(currentPageNo = null | currentPageNo = 0) currentPageNo = 1; if(pageSize = null) pageSize = 2; SalarySetPage pager = empSalarySetService.getSalarySetPageByOrgIdx(getTenantId(), currentPageNo, pageSize, orgId); return pager; ,代码的坏味道之IF语句,5.读不懂 public String getDetaliOrgRoute(Long orgIdx, String orgName, String prefix) Organization org = orgDataService.getOrgById(getTenantId(), orgIdx); if(org.getUplink()!=0) Organization fatherOrg = orgDataService.getOrgById(getTenantId(),org.getUplink(); orgName = fatherOrg.getOrgName() + prefix + orgName; return getDetaliOrgRoute(fatherOrg.getIdx(), orgName, prefix); else return orgName; ,代码的坏味道之IF语句,5.难以理解 List list = roleJobService.getOrgRoleTypeByCode(tenantId,cod); if (list = null | list.size() = 0) return true; else for (OrgRoleType rgRoleType : list) if(rgRoleType.getIdx()=main.getIdx() return true; return false; ,代码的坏味道之IF语句,6.多此一举,if (list = null | list.size() = 0) return true; else return false; ,7.可以简化,if(size0) mail.setIsAttached(1); else mail.setIsAttached(0);.,代码的坏味道之IF语句,8.永远不会执行的条件 if (lis != null ,代码的坏味道之IF语句,9.错误的思路 public void uploadPhoto(RequestParam(“file“) CommonsMultipartFile file,Long id, HttpServletResponse response) if (file != null) String errorStr = null; FTPUtil ftpUtil = new FTPUtil(); try if (!fileName.toLowerCase().endsWith(“.jpg“) .,代码的坏味道之IF语句,10.IF语句带来整个逻辑的复杂 public List getEntryOrgAndCount(Long empIdx) StringBuffer sql = new StringBuffer(“ select edt.deptIdx, count(*) as deptCount from eb_deploy_task edt where 1=1 “); if(empIdx != null) sql.append(“ and edt.empIdx = “ + empIdx); sql.append(“ and edt.status = 10 “); sql.append(“ group by edt.deptIdx “); List list = deployTaskDao.findBySQL(sql.toString(); return list; else return null; ,代码的坏味道之IF语句,11.重复的IF语句 if (sex != 0) query.append(“ AND sex:“ + sex ); if (resumeFrom != 0) query.append(“ AND RESUME_FROM:“ + resumeFrom ); if(residencyType != 0) query.append(“ AND RESIDENCY_TYPE:“ + residencyType ); if(contractStatus != 0) query.append(“ AND CONTRACT_STATUS:“ + contractStatus ); if(contractType !=0) query.append(“ AND CONTRACT_TYPE:“ + contractType ); if(pop != 0 ) query.append(“ AND pop:“ + pop ); if(religion != 0) query.append(“ AND RELIGION:“ + religion ); if(race != 0) query.append(“ AND RACE:“ + race ); if(nationality != 0) query.append(“ AND NATIONALITY:“ + nationality ); if(ethnic != 0) query.append(“ AND ETHNIC:“ + ethnic );,代码的坏味道之IF语句,12.IF语句的扩展性问题 public ResponseBody Pager findJobComments(Long companyId,Long jobId,Integer type,Integer pageNo,Integer w) long userId = getUser().getId(); if (pageNo = null) pageNo = 0; Pager pager = null; if(type =0) pager = jobCommentSerice.findMyJobsComments(userId, jobId, type, pageNo,w); return pager; else if(type =1) pager = companyCommentService.findMyCompanyComments(userId, companyId, type,pageNo,w); return pager; return null; ,代码的坏味道之FOR循环,1.不该存在的FOR循环，排序 /* * 按empcode排序方法 * param group * return */ public static List sortByEmpcode( List group) List groupEmp = new ArrayList(); EmployeePosition postion; for (int m = 0; m group.size(); m+) boolean flag = true; postion = group.get(m); for (int n = 0; n groupEmp.size(); n+) if (!compareToEmpcode(postion.getEmp().getEmpCode(), groupEmp .get(n).getEmp().getEmpCode() groupEmp.add(n, postion); flag = false; break; if (flag) groupEmp.add(postion); return groupEmp; ,代码的坏味道之FOR循环,1.不该存在的FOR循环，排序问题 if(jobMains != null ,代码的坏味道之FOR循环,2.多重循环 for (int k = 0; k orgJobMains = orgDataService.getOrgJobMainByOrgId(tenantId, orgs.get(k).idx); if(stdJobs != null) for (int j = 0; j stdJobs.size(); j+) if(stdJobs.get(j).status != 1L) isOk = false; if(orgJobMains != null) for (int i = 0; i orgJobMains.size(); i+) if(stdJobs.get(j).getIdx() = orgJobMains.get(i).uplink | (orgs.get(k).getOrgName() + stdJobs.get(j).jobName ).equals(orgJobMains.get(i).jobName) isOk = false; if(isOk) OrgJobMain jobMain = new OrgJobMain(); jobMain.setUpdateBy(getUser().getIdx(); jobMain.setLayer(stdJobs.get(j).layer); String reCode = PinYinUtil.converterToFirstSpell(jobMain.jobName).toUpperCase(); isOk = true;,代码的坏味道之FOR循环,3.查找 boolean exist = false; for(EmpSalaryDetail detail: details) if(detail.getPackageType() = packageTypesi ,4. 难以理解的循环 for(int i = 0;iroleNoChanelUp.size();i+) if(roleNoChanelUp.get(i).getUnderDept().getUplink() = 0 ) roleNoChanelUp.remove(i); i = i-1; ,代码的坏味道之FOR循环,5.分层错误 if(list = null | list.size() = 0) ,代码的坏味道之FOR循环,6.没有必要的循环 JSONArray roleMainJSONArray = if(roleNoChanelUp != null ,7.循环补全 int companyIdStrLength = corpIdx.length(); for (int i = 0; i 6 - companyIdStrLength; i+) corpIdx = “0“ + corpIdx; .,代码的坏味道之FOR循环,8.集合删除 for (int i = roleMains.size() - 1; i = 0; i-) orgRoleMain = roleMains.get(i); if (sta = 1 ,圈复杂度,圈复杂度是一种度量方法。 由Thomas McCabe于1975年定义. 圈复杂度是一个方法中执行路径的数量。,圈复杂度（Cyclomatic Complexity，CC）,圈复杂度（Cyclomatic Complexity，CC）,计算程序中的圈复杂度 1. 从1开始，一直往下通过程序,计算程序中的圈复杂度 2. 一旦遇到以下的关键字，或者其他同类词，加1（if/while/for/and/or）,圈复杂度（Cyclomatic Complexity，CC）,计算程序中的圈复杂度 3. 给case语句中的每一种情况加1,圈复杂度（Cyclomatic Complexity，CC）,例子,RequestMapping(value = “/editPage“, method = RequestMethod.POST) public ResponseBody JSONMessage editPage(OrgJobMain orgJobMain) OrgJobMain jobMain1 = positionService.getOrgJobMainById(getUser().getTenantId(), orgJobMain.getIdx(); JSONMessage message = new JSONMessage(); if(jobMain1.jobCode != null j+) if(jobMains.get(i).layer = jobMains.get(j).layer),圈复杂度（Cyclomatic Complexity，CC）,例子,if(jobMains.get(i).getJobCode() != null ,圈复杂度（Cyclomatic Complexity，CC）,例子,if(i 0 ,圈复杂度（Cyclomatic Complexity，CC）,例子,jobMain1.setEffectiveDate(orgJobMain.getEffectiveDate() != null ,圈复杂度（Cyclomatic Complexity，CC）,例子,RequestMapping(value = “/editPage“, method = RequestMethod.POST) public ResponseBody JSONMessage editPage(OrgJobMain orgJobMain) OrgJobMain jobMain1 = positionService.getOrgJobMainById(getUser().getTenantId(), orgJobMain.getIdx(); 1 JSONMessage message = new JSONMessage(); 3 if(jobMain1.jobCode != null j+) 8 if(jobMains.get(i).layer = jobMains.get(j).layer),圈复杂度（Cyclomatic Complexity，CC）,例子,10 if(jobMains.get(i).getJobCode() != null ,圈复杂度（Cyclomatic Complexity，CC）,例子,21 if(i 0 ,圈复杂度（Cyclomatic Complexity，CC）,例子,25 jobMain1.setEffectiveDate(orgJobMain.getEffectiveDate() != null ,圈复杂度（Cyclomatic Complexity，CC）,学术成果,学术成果,圈复杂度,过去几年的各种研究已经确定： 圈复杂度大于10的方法存在很大的出错风险。 1-4 is low complexity， 5-7 indicates moderate complexity, 8-10 is high complexity, and 11+ is very high complexity.,圈复杂度,正常的程序员看上去很难处理好5-9个以上的智力实体，并且提高的可能性不大，因此，你只能减低你程序的复杂度。 Miller 1995,圈复杂度（Cyclomatic Complexity，CC）,解决之道,for (EmployeePosition ep : employeePositionList) empMap.put(ep.getEmp().getIdx(), ep.getEmp(); empList.addAll(empMap.values();,1.集合返回非null对象 if (employeePositionList != null ,代码的坏味道之IF语句,2.使用卫语句 byte bufKey = RedisCacheInterceptor. stringSerializer.serialize(session.getId(); byte bufValue = connection.get(bufKey); if (bufValue != null) try return RedisCacheInterceptor. javaSerializer.deserializeInto(bufValue, session); catch (IOException e) e.printStackTrace(); catch (ClassNotFoundException e) e.printStackTrace(); return null;,代码的坏味道之IF语句,2.使用卫语句 byte bufKey = RedisCacheInterceptor. stringSerializer.serialize(session.getId(); byte bufValue = connection.get(bufKey); if (bufValue != null) return null; try return RedisCacheInterceptor. javaSerializer.deserializeInto(bufValue, session); catch (IOException e) e.printStackTrace(); catch (ClassNotFoundException e) e.printStackTrace(); return null;,代码的坏味道之IF语句,2.使用卫语句 if (orgId != null) List employeePositionList =orgDataService .getEmployeePositionByOrgId(getTenantId(), orgId); Map empMap = new HashMap(); List empList = new ArrayList(); if (employeePositionList != null ,代码的坏味道之IF语句,2.使用卫语句 if (orgId != null) pager.setSuccess(false); return; List employeePositionList =orgDataService .getEmployeePositionByOrgId(getTenantId(), orgId); Map empMap = new HashMap(); List empList = new ArrayList(); for (EmployeePosition ep : employeePositionList) empMap.put(ep.getEmp().getIdx(), ep.getEmp(); empList.addAll(empMap.values(); empList = EmployeeMainSorter.sortByEmpcode(empList); pager.setRoot(empList); pager.setSuccess(true);,代码的坏味道之IF语句,3.使用默认值 public ResponseBody SalarySetPage getList(Integer currentPageNo, Integer pageSize, Long orgId) (“EmpTreatmentController.getList()“); if(currentPageNo = null | currentPageNo = 0) currentPageNo = 1; if(pageSize = null) pageSize = 2; SalarySetPage pager = empSalarySetService.getSalarySetPageByOrgIdx(getTenantId(), currentPageNo, pageSize, orgId); return pager; ,代码的坏味道之IF语句,3.使用默认值 public ResponseBody SalarySetPage getList(Integer currentPageNo, Integer pageSize, Long orgId) (“EmpTreatmentController.getList()“); if(currentPageNo = null | currentPageNo = 0) currentPageNo = 1; if(pageSize = null) pageSize = 2; SalarySetPage pager = empSalarySetService.getSalarySetPageByOrgIdx(getTenantId(), currentPageNo, pageSize, orgId); return pager; ,代码的坏味道之IF语句,3.使用默认值 public class Page private Integer currentPageNo = 1; private Integer pageSize = 2; public ResponseBody SalarySetPage getList(Page currPage, Long orgId) (“EmpTreatmentController.getList()“); SalarySetPage pager = empSalarySetService.getSalarySetPageByOrgIdx(getTenantId(), currPage.getCurrentPageNo(), currPage.getPageSize(), orgId); return pager; ,代码的坏味道之IF语句,4.使用容易理解的临时变量 public String getDetaliOrgRoute(Long orgIdx, String orgName, String prefix) Organization org = orgDataService.getOrgById(getTenantId(), orgIdx); if(org.getUplink()!=0) Organization fatherOrg = orgDataService.getOrgById(getTenantId(),org.getUplink(); orgName = fatherOrg.getOrgName() + prefix + orgName; return getDetaliOrgRoute(fatherOrg.getIdx(), orgName, prefix); else return orgName; ,代码的坏味道之IF语句,4.使用容易理解的临时变量 public String getDetaliOrgRoute(Long orgIdx, String orgName, String prefix) Organization org = orgDataService.getOrgById(getTenantId(), orgIdx); boolean isSuperiorOrg = org.getUplink() = 0; if(isSuperiorOrg) return orgName; Organization fatherOrg = orgDataService.getOrgById(getTenantId(),org.getUplink(); orgName = fatherOrg.getOrgName() + prefix + orgName; return getDetaliOrgRoute(fatherOrg.getIdx(), orgName, prefix); ,代码的坏味道之IF语句,5.综合修改 List list = roleJobService.getOrgRoleTypeByCode(tenantId,cod); if (list = null | list.size() = 0) return true; else for (OrgRoleType rgRoleType : list) if(rgRoleType.getIdx()=main.getIdx() return true; return false; ,代码的坏味道之IF语句,5.综合修改 List list = roleJobService.getOrgRoleTypeByCode(tenantId,cod); if ( list.size() = 0) return true; for (OrgRoleType rgRoleType : list) if(rgRoleType.getIdx()=main.getIdx() return true; return false;,解决之道,return list = null | list.size() = 0;,6.直接返回 if (list = null | list.size() = 0) return true; else return false; ,解决之道,mail.setIsAttached(size0?1:0);,7.使用表达式 if(size0) mail.setIsAttached(1); else mail.setIsAttached(0);,代码的坏味道之IF语句,8.用返回代替判断 public void uploadPhoto(RequestParam(“file“) CommonsMultipartFile file,Long id, HttpServletResponse response) if (file != null) String errorStr = null; FTPUtil ftpUtil = new FTPUtil(); try if (!fileName.toLowerCase().endsWith(“.jpg“) .,代码的坏味道之IF语句,8.用返回代替判断 public void uploadPhoto(RequestParam(“file“) CommonsMultipartFile file,Long id, HttpServletResponse response) if (file != null) String errorStr = null; FTPUtil ftpUtil = new FTPUtil(); try if (!fileName.toLowerCase().endsWith(“.jpg“) ,代码的坏味道之IF语句,9.直接返回+表达式 public List getEntryOrgAndCount(Long empIdx) StringBuffer sql = new StringBuffer(“ select edt.deptIdx, count(*) as deptCount from eb_deploy_task edt where 1=1 “); if(empIdx != null) sql.append(“ and edt.empIdx = “ + empIdx); sql.append(“ and edt.status = 10 “); sql.append(“ group by edt.deptIdx “); List list = deployTaskDao.findBySQL(sql.toString(); return list; else return null; ,代码的坏味道之IF语句,9.直接返回+表达式 public List getEntryOrgAndCount(Long empIdx) if(empIdx = null) return null; String sql = “ select edt.deptIdx, count(*) as deptCount from eb_deploy_task edt where edt.empIdx = ? and edt.status = 10 group by edt.deptIdx“; List list = deployTaskDao.findBySQL(sql,empIdx); return list;,代码的坏味道之IF语句,10.使用循环代替重复的IF语句 if (sex != 0) query.append(“ AND sex:“ + sex ); if (resumeFrom != 0) query.append(“ AND RESUME_FROM:“ + resumeFrom ); if(residencyType != 0) query.append(“ AND RESIDENCY_TYPE:“ + residencyType ); if(contractStatus != 0) query.append(“ AND CONTRACT_STATUS:“ + contractStatus ); if(contractType !=0) query.append(“ AND CONTRACT_TYPE:“ + contractType ); if(pop != 0 ) query.append(“ AND pop:“ + pop ); if(religion != 0) query.append(“ AND RELIGION:“ + religion ); if(race != 0) query.append(“ AND RACE:“ + race ); if(nationality != 0) query.append(“ AND NATIONALITY:“ + nationality ); if(ethnic != 0) query.append(“ AND ETHNIC:“ + ethnic );,代码的坏味道之IF语句,10.使用循环代替重复的IF语句 String keyWords = new String“ AND sex:“,“ AND RESUME_FROM:“, “ AND RESIDENCY_TYPE:“,“ AND CONTRACT_STATUS:“,“ AND CONTRACT_TYPE:“, “ AND pop:“,“ AND RELIGION:“,“ AND RACE:“,“ AND NATIONALITY:“, “ AND ETHNIC:“; int valueWords = new intsex,resumeFrom,residencyType,contractStatus,contractStatus, contractType,pop,religion,race,nationality,ethnic; for(int i=0;ikeyWord.size();i+) if(valueWordsi != 0) query.append(keyWordsi+valueWordsi); ,代码的坏味道之IF语句,11.使用对象解决IF语句扩展问题 public ResponseBody Pager findJobComments(Long companyId,Long jobId,Integer type,Integer pageNo,Integer w) long userId = getUser().getId(); if (pageNo = null) pageNo = 0; Pager pager = null; if(type =0) pager = jobCommentSerice.findMyJobsComments(userId, jobId, type, pageNo,w); return pager; else if(type =1) pager = companyCommentService.findMyCompanyComments(userId, companyId, type,pageNo,w); return pager; return null; ,代码的坏味道之IF语句,11.使用对象解决IF语句扩展问题 public class PagerGetter public Pager getPager(Integer userId,Long jobId,Integer type,Page page); public Pager JobCommentPager implements PagerGetter public Pager getPager(Integer userId,Long jobId,Integer type,Page page) return jobCommentSerice.findMyJobsComments(userId, jobId, type, page.getPageNo,page.getW()a); ,代码的坏味道之IF语句,11.使用对象解决IF语句扩展问题 public Pager CompanyCommentPager implements PagerGetter public Pager getPager(Integer userId,Long jobId,Integer type,Page page) return companyCommentSerice.findMyJobsComments(userId, jobId, type, page.getPageNo,page.getW()a); public class PagerGetterFactory public static PagerGetter getPagerGetter(Integer type) if(type=0) return new JobCommentPager(); else if(type = 1) return new CompanyCommentPager(); ,代码的坏味道之IF语句,11.使用对象解决IF语句扩展问题 public ResponseBody Pager findJobComments(Long companyId,Long jobId,Integer type,Integer pageNo,Integer w) long userId = getUser().getId(); if (pageNo = null) pageNo = 0; PagerGetter pg = PagerGetterFactory.getPagerGetter(type); return pg.getPager(userId,jobId,type,new Pager(pageNo,w); return null; ,代码的坏味道之IF语句,11.使用对象解决IF语句扩展问题 进一步的扩展，type设定为类名： public class PagerGetterFactory public static PagerGetter getPagerGetter(Integer type) return (PagerGetter)Class.forName(type).newInstance(); ,代码的坏味道之FOR循环,1.使用API /* * 按empcode排序方法 * param group * return */ public static List sortByEmpcode( List group) List groupEmp = new ArrayList(); EmployeePosition postion; for (int m = 0; m group.size(); m+) boolean flag = true; postion = group.get(m); for (int n = 0; n groupEmp.size(); n+) if (!compareToEmpcode(postion.getEmp().getEmpCode(), groupEmp .get(n).getEmp().getEmpCode() groupEmp.add(n, postion); flag = false; break; if (flag) groupEmp.add(postion); return groupEmp; ,代码的坏味道之FOR循环,1.使用API /* * 按empcode排序方法 * param group * return */ public static void sortByEmpcode( List group) Collections.sort(list1, new Comparator() public int compare(EmployeePosition o1, EmployeePosition o2) return compareToEmpcode(postion.getEmp().getEmpCode(), groupEmp .get(n).getEmp().getEmpCode() ; ); ,代码的坏味道之FOR循环,注意：数组也有sort API 在Arrays类里。,注意：类似的方法 在Collections类和Arrays类里，有这样一些方法： 1.binarySearch 2.max 3.min 4. frequency 5. Reverse 请使用这些方法来避免不必要的FOR循环，谢谢！,代码的坏味道之FOR循环,其他一些避免FOR循环的方法 1.求两个集合的并集 addAlll 2.求两个集合的交集 retain