课题修改PMD总结.docx

1、课题修改PMD总结修改PMD总结1.Avoid unnecessary Comparisons in Boolean exception.(Boolean类型重复判断)错误 例子: if(null! = a & a.size0) 正确 if(null! = a & false = a.IsEmpay()2. Avoid Using implementation types like (ArrayList HashMap/ LinkedHashMap) ,use the interface instand.(用数组的接口类型) 错误 例子:ArrayList arraylist=new Arra

2、yList(); 正确 List list=new ArrayList();错误 例子: private static HashMap map=new HashMap(); 正确 private static Map map=new HashMap(); 错误 例子: private static LinkedHashMap map=new LinkedHashMap(); 正确 private static Map map=new LinkedHashMap(); 3. Method names should not start with capital letters(方法名不能以大写开头

3、)。错误 例子: public class Start()正确 public class start() 可以用快捷键 Alt+shift+R全部替4.varivable that are final and static should be in all caps.(定义的参数必须大写)错误 例子:public static final String root正确 public static final String ROOT5.Avoid appending charcutars as Strings in StringBuffer append (避免在StringBuffer里附加单个

4、字符时附加成String类型)错误 例子: buf.append(“)”)或者buf.append(“a”)正确 buf.append()或者 buf.append(a)6.use ArrayList instanded of vector(使用ArrayList替换vector后还是会报错，所以直接改成是以它的接口形式替换)错误 例子: vector keys = new vector(ELE);正确 List keys = new ArrayList(ELE); 7. Variables that are not final should not contain underscores (

5、except for underscores in standard prefix/suffix) (变量不是final类型的不能包含下划线)错误 例子: private int DEAULT_PORT = 8001;正确 private int DEAULTPORT = 8001;(调用它的所有类都需要改动)8. Variables should start with a lowercase character(参数必须要以小写开始)错误 例子: private static int HANDLE_MAX = 200;正确 private static int handleMax = 200

6、; 9. Using equalsIgnoreCase() is cleaner than using toUpperCase/toLowerCase().equals().错误 例子: 正确10. Unnecessary wrapper object creation 错误 例子: intCurPage = Integer.valueOf(curPage).intValue();正确 intCurPage = Integer.parseInt(curPage);11. This is an inefficient use of StringBuffer.toString; call Stri

7、ngBuffer.length instead. 错误 If(newPartLen+smsMOCommondArr.toString().getBytes(DB_CHARSET).length DB_VERCHAR_MAX_LEN + 1) 正确 if(newPartLen+(smsMOCommondArr.toString().getBytes(DB_CHARSET).length DB_VERCHAR_MAX_LEN + 1) 12. This final field could be made static错误 例子: private final String urlPrefix = h

8、ttp:/;正确 private static final String URL_PREFIX = http:/;13. The field name indicates a constant but its modifiers do not错误 例子: private static String CONF_NAME = version;正确 private static final String CONF_NAME = version;14. System.out.print is used错误 例子: System.out.println(PartalOneAppender-message

9、=+message+);正确 /System.out.println(PartalOneAppender-message=+message+);15. Switch statements should have a default label错误 例子: switch (Type) case USER: displayType = USER; break; case ADMIN: displayType = ADMIN; break； 正确 switch (Type) case USER: displayType = USER; break; case ADMIN: displayType =

10、 ADMIN; break; default: 16. Substitute calls to size() = 0 (or size() != 0) with calls to isEmpty()错误 例子: if(null=Handlers | 0 =Handlers.size()正确 if (null=Handlers | Handlers.isEmpty()17. Return an empty array rather than null.错误 例子: if (null != g & g.length 0) String cloneGroups = new Stringg.lengt

11、h; System.arraycopy(g, 0, cloneGroups, 0, g.length); return cloneGroups; return null;正确 if (null != g & g.length 0) String cloneGroups = new Stringg.length; System.arraycopy(g, 0, cloneGroups, 0, g.length); return cloneGroups; return new String0;18. Deeply nested if.then statements are hard to read原

12、因: 深嵌套的if循环很难读懂。报错例子 if (null != portalScriptionInfo & null != portalScriptionInfo.getChargeInfo()if(productId.equals(portalScriptionInfo.getChargeInfo().getSourceChargeId()/ 构造orderInfo 对象portalOrderInfo.setProductId(productId);productName = chargeInfo.getProductName();break; 修改后的例子 if (null != por

13、talScriptionInfo& null !=portalScriptionInfo.getChargeInfo()& (productId.equals(portalScriptionInfo.getChargeInfo() .getSourceChargeId() portalOrderInfo.setProductId(productId); productName = chargeInfo.getProductName(); break;19. Caught exception is rethrown, original stack trace may be lost原因: 捕捉一

14、个异常后，再从新把异常扔出去，会把以前的异常信息丢掉。修改: 可以把在此扔出的异常信息以Log日志的形式打印出来。 例如: (错误) catch (IOException ioe) String msg = Cant open config file: + xmlFile + due to: + ioe; throw new IOException(msg); 改正后：catch (IOException ioe) String msg = Cant open config file: + xmlFile + due to: + ioe;LogFactory.getInstance().log

15、Action(msg); 20.Avoid throwing raw Exception types(避免抛出一个生疏的异常类型)错误 例子: catch (IOException ioe) ioe.printStackTrace();String msg = Cant open config file: + xmlFile.getAbsolutePath()+ due to: + ioe; throw new Exception(msg);正确 catch (IOException ioe) ioe.printStackTrace();String msg = Cant open confi

16、g file: + xmlFile.getAbsolutePath()+ due to: + ioe;LogFactory.getInstance().logAction(msg); 21. Method call on object which may be null错误 例子: if (GroupList = null & GroupList.size() 1)正确 if (GroupList.isEmpty()22. It is somewhat confusing to have a field name with the same name as a method.原因：A getX

17、() method which returns a boolean should be named isX() 属性名与方法名称相似。修改：错误 private boolean stopServer; public void stopServer() this.stopServer = true; 正确 可以把方法名称该换一个名字！ 23. Do not use if statements that are always true or always false原因: 不要总使用If循环条件是true或者是false。修改: (错误的)String NameKey = request.getP

18、arameter(NameKey);if (true) request.setAttribute(NameKey, nameKey); ReleaseContent releaseContent = new ReleaseContent(); releaseContent.setCatalogId(catalogId); User user= super.getUser(request); int userType = userInfo.getUserType(); (正确的)ift条件是真的就可以去掉if(true) String NameKey = request.getParameter

19、(NameKey);/if (true) request.setAttribute(NameKey, nameKey); ReleaseContent releaseContent = new ReleaseContent(); releaseContent.setCatalogId(catalogId); User user= super.getUser(request); int userType = userInfo.getUserType(); 24. System.arraycopy is more efficient报错的例子: for (int i1 = 0; i1 tmpabc

20、de.length; i1+) tmpabcdei1 = digestInti1; 修改成 for (int i1 = 0; i1 tmpabcde.length; i1+) / tmpabcdei1 = digestInti1; System.arraycopy(digestInt, i1, tmpabcde, i1, 1); * arraycopy(Objectsrc, intsrcPos, Objectdest, intdestPos, intlength) 从指定源数组中复制一个数组，复制从指定的位置开始，到目标数组的指定位置结束。参数： src - 源数组。 srcPos - 源数组

21、中的起始位置。 dest - 目标数组。 destPos - 目标数据中的起始位置。 length - 要复制的数组元素的数量。 25.use aslist instended of tight loops()原因 for (int i = 0; i type.length; i+) List.add(type i); 修改： List = Arrays.asList(type);* 提供了一个创建固定长度的列表的便捷方法，该列表被初始化为包含多个元素：List list= Arrays.asList(Larry, Moe, Curly);参数：Larry : 存放的类型 Moe: 有效性 c

22、urly:26.Avoid empty if statements() 原因：在if循环中没有大括号。做法：错误 例子: if (mlang = null) mlang = LanguageUtil.getDefaultLanguage(); return _ + mlang.getLanguage().toUpperCase() + _ + mlang.getCountry().toUpperCase();正确 if (mlang = null) mlang = LanguageUtil.getDefaultLanguage(); return _ + mlang.getLanguage()

23、.toUpperCase() + _ + mlang.getCountry().toUpperCase();27. Avoid using (if.else/ if/ for/ while) statements without curly braces原因: 避免使用(if.else/ if/ for/ while)循环时没有波形括号(基本的语法错误)修改: 应该加括号的地方加上括号。28. Avoid using exceptions as flow control.原因: 避免使用异常来控制流程修改: 报出的异常信息基本上都是在try。catch。的catch语句块中,可以把在catch

24、语句块中抛出的异常信息，用log日志来代替输出信息。29. Avoid unnecessary if.then.else statements when returning a Boolean原因: 在返回值是Boolean类型时，避免不必要的使用if.then.else修改： 错误的：if (UserConstant.TYPE_SP = getUser(request).getUserType() return true; else return false; 正确的：if (UserConstant.TYPE_SP = getUser(request).getUserType() retu

25、rn true; return false; 30. Avoid unnecessary constructors - the compiler will generate these for you.原因: 产生了一个多余的构造器，编辑器将为你产生它们。做法: 一个公有的抽象类，不需要自己在写一个构造器，因为它本身自己就可以提供构造方法。删除多余的私有构造方法。31. Avoid instantiating Boolean objects; reference Boolean.TRUE or Boolean.FALSE or call Boolean.valueOf() instead.错误

26、 例子: request.setAttribute(productNotFound, Boolean.valueOf(true);正确 request.setAttribute(productNotFound, Boolean.TRUE);*Boolean类型的值不需要值类型转换，直接可以赋以true或者是false；32. Avoid catching NullPointerException; consider removing the cause of the NPE.原因：避免捕捉产生的空指针(排除由它造成的NPE原因)做法: 删除语句块中抛出的异常信息，由Log日志来带它打印信息33

27、. Avoid calling toString() on String objects; this is unnecessary.错误 例子: String result = ;return result.toString();正确 return result;* 本来就是String类型不需要再toString()转换;34. An empty statement (semicolon) not part of a loop.原因: if (is != null) try is.close(); catch (Throwable u) ; 正确 如果该方法没有任何的代码，你就可以使用日志来

28、记录它的异常信息。35. A throw statement in a finally block makes the control flow hard to understand.原因：不要在finally语句块中抛出异常，会造成一个很难理解的控制流。做法：可以把抛出的异常信息，用log日志的形式来替换。36. Avoid really (long/short) parameter lists.原因：方法参数名太长。 做法：37. No need to import a type that lives in the same package原因：不需要导入类型相识的架包。做法：使出这个多余

29、的架包。 38. No need to call String.valueOf to append to a string.原因: 它把String类型的值再一次转化为String类型的值，是多余的。做法： 不用转化它的值类型，因为它本身就是String类型的值。 39. A method/constructor shouldnt explicitly throw java.lang.Exception原因：方法不能扔出一个不具体的异常信息。做法：根据具体的代码，抛出具体的异常信息。40. Avoid using implementation typelike( TreeMap/java.ut

30、il.HashSet/java.util.HashSet) use the interface instead错误 例子:TreeMap map=NEW TreeMap();正确 Map map=NEW TreeMap();41. Avoid unused imports such as org.apache.struts.action.ActionMessages原因: 导入了多余的架包，例如：org.apache.struts.action.ActionMessages做法：删除掉。同时也可以用快捷键先ctrl+A，再ctrl+shift+o就可以了。 42. Avoid returning from a finally block原因: 返回信息在fina