FindBugs常見問題指南1

ComparisonofStringobjectsusing==or!=例，overrideequals方法時(shí)容易犯錯(cuò)Java代碼

\o"收藏這段代碼"if(this.topic

!=

key.getTopic())

return

false;2DeadstoretonewStatusRecord

定義局部變量后沒有引用3InvocationoftoStringonvalues

直接調(diào)用數(shù)組的toString方法Java代碼

\o"收藏這段代碼"public

Query

createQuery(String

hql,

Object

values[],Session

session){

logger.debug(values);

logger.debug((new

StringBuilder()).append("hql=[").append(hql).append("]

").append(((Object)

}

正確的例子，調(diào)用Arrays.toString()和Arrays.deepToString()方法。Java代碼

\o"收藏這段代碼"

import

java.util.Arrays;

class

A{

}

class

B{

@Override

public

String

toString()

{

return

"BBBBB";

}

}

public

class

Test

{

public

static

void

main(String[]

args)

{

Object

[]

a

=

{new

Integer(0),new

Boolean(true),true,new

A(),new

B()};

Object[][]b

={{new

A(),new

B()},{new

A(),new

B()},{new

A(),new

B()}};

System.out.println(Arrays.deepToString(b));

}

}

4ignoresexceptionalreturnvalueofjava.io.File.mkdirs()

忽略了返回值，應(yīng)當(dāng)含有返回值Java代碼

\o"收藏這段代碼"public

void

initFolder()

{

(!exitDir.isDirectory())

{

exitDir.mkdirs();

("===Finishing

create

exit

trade

image

folder!====");

}

Thismethodreturnsavaluethatisnotchecked.Thereturnvalueshouldbecheckedsinceitcanindicateanunusualorunexpectedfunctionexecution.Forexample,theFile.delete()methodreturnsfalseifthefilecouldnotbesuccessfullydeleted(ratherthanthrowinganException).Ifyoudon'tchecktheresult,youwon'tnoticeifthemethodinvocationsignalsunexpectedbehaviorbyreturninganatypicalreturnvalue.5不使用newString()定義空的字符串Java代碼

\o"收藏這段代碼"String

alarmCodeCond

=

new

String();

應(yīng)當(dāng)

Java代碼

\o"收藏這段代碼"String

alarmCodeCond

=

"";

例：

Java代碼

\o"收藏這段代碼"public

void

method1()

{

String

ip

=

null;

try

{

ip

=

InetAddress.getLocalHost().getHostAddress();

}

catch

(UnknownHostException

e)

{

e.printStackTrace();

}

long

ipCount

=

countIpAddress(ip);

//

可能會(huì)傳入空引用

//...

}

long

countIpAddress(String

ip)

{

long

ipNum

=

0;

String[]

ipArray

=

ip.split("\\.");

}

修改后：Java代碼

\o"收藏這段代碼"public

void

method1()

{

String

ip

=

null;

try

{

ip

=

InetAddress.getLocalHost().getHostAddress();

}

catch

(UnknownHostException

e)

{

e.printStackTrace();

}

long

ipCount

=

countIpAddress(ip);

//

可能會(huì)傳入空引用

//...

}

long

countIpAddress(String

ip)

{

long

ipNum

=

0;

if

(ip

==

null)

{

return

0;

//或者拋出異常

}

String[]

ipArray

=

ip.split("\\.");

//...

}

注意：函數(shù)入口需要交驗(yàn)入?yún)⒌暮戏ㄐ浴?3Methodconcatenatesstringsusing+inaloop

在循環(huán)里使用字符串連接，效率低，應(yīng)該使用StringBuilder/StringBuffer

例：

Java代碼

\o"收藏這段代碼"String

writeData

=

"";

for

(int

i

=

0;

i

<

10;

i++)

{

writeData

=

writeData

+

"a";

}

14Methodmayfailtoclosedatabaseresource

沒有釋放數(shù)據(jù)庫資源Java代碼

\o"收藏這段代碼"public

ResultSet

callProcedure(String

procedure)

{

Session

ses

=

getSessionForUpdate();

ResultSet

rs

=

null;

try

{

Connection

conn

=

ses.connection();

conn.setAutoCommit(false);

CallableStatement

statement

=

conn.prepareCall(procedure);

//may

fail

to

close

CallableStatement

rs

=

statement.executeQuery();

mit();

}

catch

(Exception

e)

{

e.printStackTrace();

}

finally

{

try

{

ses.close();

}

catch

(SQLException

e)

{

throw

e;

}

}

return

rs;

}

應(yīng)當(dāng)修改為：

Java代碼

\o"收藏這段代碼"public

ResultSet

callProcedure(String

procedure)

{

Session

ses

=

getSessionForUpdate();

ResultSet

rs

=

null;

CallableStatement

statement

=

null;

try

{

Connection

conn

=

ses.connection();

conn.setAutoCommit(false);

statement

=

conn.prepareCall(procedure);

rs

=

statement.executeQuery();

mit();

}

catch

(Exception

e)

{

e.printStackTrace();

}

finally

{

try

{

statement.close();

ses.close();

}

catch

(SQLException

e)

{

e.printStackTrace();

}

}

return

rs;

}

15Methodmayfailtoclosestream

沒有關(guān)閉流，可能會(huì)導(dǎo)致文件描述符泄露，應(yīng)該在finally中關(guān)閉

例：Java代碼

\o"收藏這段代碼"try

{

FileInputStream

in

=

new

FileInputStream(file);

InputStreamReader

inputStreamReader

=

new

InputStreamReader(in);

BufferedReader

reader

=

new

BufferedReader(inputStreamReader);

//...

in.close();

inputStreamReader.close();

reader.close();

}

catch

(IOException

e)

{

}

修改為：Java代碼

\o"收藏這段代碼"FileInputStream

in

=

null;

InputStreamReader

inputStreamReader

=

null;

BufferedReader

reader

=

null;

try

{

in

=

new

FileInputStream(file);

inputStreamReader

=

new

InputStreamReader(in);

reader

=

new

BufferedReader(inputStreamReader);

//

...

}

catch

(IOException

e)

{

}

finally

{

try

{

in.close();

}

catch

(IOException

e)

{

e.printStackTrace();

}

try

{

inputStreamReader.close();

}

catch

(IOException

e)

{

e.printStackTrace();

}

try

{

reader.close();

}

catch

(IOException

e)

{

e.printStackTrace();

}

}

16Methodmightignoreexception

Thismethodmightignoreanexception.

Ingeneral,exceptionsshouldbehandledorreportedinsomeway,ortheyshouldbethrownoutofthemethod.應(yīng)該將異常處理、打印或者拋出反例：Java代碼

\o"收藏這段代碼"try

{

//...

}

catch

(Exception

e)

{

}

17Classdefinesnon-transientnon-serializableinstancefieldreaderTypeInfo

一個(gè)實(shí)現(xiàn)了Serializable接口的類，含有非transient和非serializable的實(shí)例對象域。

ThisSerializableclassdefinesanon-primitiveinstancefieldwhichisneithertransient,Serializable,orjava.lang.Object,anddoesnotappeartoimplementtheExternalizableinterfaceorthereadObject()andwriteObject()methods.

Objectsofthisclasswillnotbedeserializedcorrectlyifanon-Serializableobjectisstoredinthisfield.18Nullcheckofvaluepreviouslydereferenced

前面獲取的對象，現(xiàn)在引用的時(shí)候沒有交驗(yàn)是否為null反例：Java代碼

\o"收藏這段代碼"Reader

reader

=

null;

try

{

reader

=

this.getReaderByName(readerBasicInfo.getByName());

}

catch

(Exception

e1)

{

e1.printStackTrace();

return

ReaderStateConst.FAIL;

}

DependenceRelation

dependenceRelation

=

new

DependenceRelation();

dependenceRelation.setDescription(reader.getIpAddress());

//

使用前沒有做null校驗(yàn)

19

Possiblenullpointerdereference

可能存在的空引用

Java代碼

\o"收藏這段代碼"capInfo

=

wrapper.wrapperToClient((ReaderCapabilities)

object);

try

{

if

(capInfo

!=

null)

{

transactionDs

.saveReaderCapabilityCom((ReaderCapabilities)

object);

}

}

catch

(RuntimeException

e)

{

capInfo.setDetailMsg(ReaderStateConst.DB_OPT_FAIL);

return

capInfo;

}

capInfo.setDetailMsg(ReaderStateConst.SUCCESSFUL);

//capInfo可能為null

20引用前需要做空校驗(yàn)Java代碼

\o"收藏這段代碼"public

synchronized

void

remove(String

batNo,

int

count)

{

List<Task>

taskList

=

commandMap.get(batNo);

synchronized

(taskList)

{

//使用前需要作null

check

//...

}

}

21Possiblenullpointerdereferenceinmethodonexceptionpath例Java代碼

List<District>

districts

=

null;

try

{

districts

=

this.getDistricts(ReaderConst.DESC);

}

catch

(Exception

e)

{

e.printStackTrace();

}

if

(start

>=

districts.size())

{

//districts

可能是null

tableData.setTotalCount(0);

return

tableData;

}

22內(nèi)部類沒有引用外部類的屬性/方法的時(shí)候，應(yīng)該作為靜態(tài)內(nèi)部類。Thisclassisaninnerclass,butdoesnotuseitsembeddedreferencetotheobjectwhichcreatedit.

Thisreferencemakestheinstancesoftheclasslarger,andmaykeepthereferencetothecreatorobjectalivelongerthannecessary.

Ifpossible,theclassshouldbemadestatic.

23包裝類的比較應(yīng)該使用eueqls，要比較值類型，需要強(qiáng)制類型轉(zhuǎn)換后再使用。Thismethodcomparestworeferencevaluesusingthe==