Class ThrowsCountCheck
- All Implemented Interfaces:
Configurable
,Contextualizable
Restricts throws statements to a specified count. Methods with "Override" or "java.lang.Override" annotation are skipped from validation as current class cannot change signature of these methods.
Rationale:
Exceptions form part of a method's interface. Declaring
a method to throw too many differently rooted
exceptions makes exception handling onerous and leads
to poor programming practices such as writing code like
catch(Exception ex)
. 4 is the empirical value which is based
on reports that we had for the ThrowsCountCheck over big projects
such as OpenJDK. This check also forces developers to put exceptions
into a hierarchy such that in the simplest
case, only one type of exception need be checked for by
a caller but any subclasses can be caught
specifically if necessary. For more information on rules
for the exceptions and their issues, see Effective Java:
Programming Language Guide Second Edition
by Joshua Bloch pages 264-273.
ignorePrivateMethods - allows to skip private methods as they do not cause problems for other classes.
-
Property
max
- Specify maximum allowed number of throws statements. Type isint
. Default value is4
. -
Property
ignorePrivateMethods
- Allow private methods to be ignored. Type isboolean
. Default value istrue
.
To configure check:
<module name="ThrowsCount"/>
Example:
class Test { public void myFunction() throws CloneNotSupportedException, ArrayIndexOutOfBoundsException, StringIndexOutOfBoundsException, IllegalStateException, NullPointerException { // violation, max allowed is 4 // body } public void myFunc() throws ArithmeticException, NumberFormatException { // ok // body } private void privateFunc() throws CloneNotSupportedException, ClassNotFoundException, IllegalAccessException, ArithmeticException, ClassCastException { // ok, private methods are ignored // body } }
To configure the check so that it doesn't allow more than two throws per method:
<module name="ThrowsCount"> <property name="max" value="2"/> </module>
Example:
class Test { public void myFunction() throws IllegalStateException, ArrayIndexOutOfBoundsException, NullPointerException { // violation, max allowed is 2 // body } public void myFunc() throws ArithmeticException, NumberFormatException { // ok // body } private void privateFunc() throws CloneNotSupportedException, ClassNotFoundException, IllegalAccessException, ArithmeticException, ClassCastException { // ok, private methods are ignored // body } }
To configure the check so that it doesn't skip private methods:
<module name="ThrowsCount"> <property name="ignorePrivateMethods" value="false"/> </module>
Example:
class Test { public void myFunction() throws CloneNotSupportedException, ArrayIndexOutOfBoundsException, StringIndexOutOfBoundsException, IllegalStateException, NullPointerException { // violation, max allowed is 4 // body } public void myFunc() throws ArithmeticException, NumberFormatException { // ok // body } private void privateFunc() throws CloneNotSupportedException, ClassNotFoundException, IllegalAccessException, ArithmeticException, ClassCastException { // violation, max allowed is 4 // body } private void func() throws IllegalStateException, NullPointerException { // ok // body } }
Parent is com.puppycrawl.tools.checkstyle.TreeWalker
Violation Message Keys:
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throws.count
- Since:
- 3.2
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Nested Class Summary
Nested classes/interfaces inherited from class com.puppycrawl.tools.checkstyle.api.AutomaticBean
AutomaticBean.OutputStreamOptions
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Field Summary
Fields -
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionint[]
The configurable token set.int[]
Returns the default token a check is interested in.int[]
The tokens that this check must be registered for.void
setIgnorePrivateMethods
(boolean ignorePrivateMethods) Setter to allow private methods to be ignored.void
setMax
(int max) Setter to specify maximum allowed number of throws statements.void
visitToken
(DetailAST ast) Called to process a token.Methods inherited from class com.puppycrawl.tools.checkstyle.api.AbstractCheck
beginTree, clearMessages, destroy, finishTree, getFileContents, getLine, getLines, getMessages, getTabWidth, getTokenNames, init, isCommentNodesRequired, leaveToken, log, log, log, setFileContents, setTabWidth, setTokens
Methods inherited from class com.puppycrawl.tools.checkstyle.api.AbstractViolationReporter
finishLocalSetup, getCustomMessages, getId, getMessageBundle, getSeverity, getSeverityLevel, setId, setSeverity
Methods inherited from class com.puppycrawl.tools.checkstyle.api.AutomaticBean
configure, contextualize, getConfiguration, setupChild
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Field Details
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MSG_KEY
A key is pointing to the warning message text in "messages.properties" file.- See Also:
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Constructor Details
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ThrowsCountCheck
public ThrowsCountCheck()Creates new instance of the check.
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Method Details
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getDefaultTokens
public int[] getDefaultTokens()Description copied from class:AbstractCheck
Returns the default token a check is interested in. Only used if the configuration for a check does not define the tokens.- Specified by:
getDefaultTokens
in classAbstractCheck
- Returns:
- the default tokens
- See Also:
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getRequiredTokens
public int[] getRequiredTokens()Description copied from class:AbstractCheck
The tokens that this check must be registered for.- Specified by:
getRequiredTokens
in classAbstractCheck
- Returns:
- the token set this must be registered for.
- See Also:
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getAcceptableTokens
public int[] getAcceptableTokens()Description copied from class:AbstractCheck
The configurable token set. Used to protect Checks against malicious users who specify an unacceptable token set in the configuration file. The default implementation returns the check's default tokens.- Specified by:
getAcceptableTokens
in classAbstractCheck
- Returns:
- the token set this check is designed for.
- See Also:
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setIgnorePrivateMethods
public void setIgnorePrivateMethods(boolean ignorePrivateMethods) Setter to allow private methods to be ignored.- Parameters:
ignorePrivateMethods
- whether private methods must be ignored.
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setMax
public void setMax(int max) Setter to specify maximum allowed number of throws statements.- Parameters:
max
- maximum allowed throws statements.
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visitToken
Description copied from class:AbstractCheck
Called to process a token.- Overrides:
visitToken
in classAbstractCheck
- Parameters:
ast
- the token to process
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