public final class ThrowsCountCheck extends AbstractCheck
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.
max
- Specify maximum allowed number of throws statements.
Type is int
.
Default value is 4
.
ignorePrivateMethods
- Allow private methods to be ignored.
Type is boolean
.
Default value is true
.
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:
throws.count
AutomaticBean.OutputStreamOptions
Modifier and Type | Field and Description |
---|---|
static String |
MSG_KEY
A key is pointing to the warning message text in "messages.properties"
file.
|
Constructor and Description |
---|
ThrowsCountCheck()
Creates new instance of the check.
|
Modifier and Type | Method and Description |
---|---|
int[] |
getAcceptableTokens()
The configurable token set.
|
int[] |
getDefaultTokens()
Returns the default token a check is interested in.
|
int[] |
getRequiredTokens()
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.
|
beginTree, clearMessages, destroy, finishTree, getFileContents, getLine, getLines, getMessages, getTabWidth, getTokenNames, init, isCommentNodesRequired, leaveToken, log, log, log, setFileContents, setTabWidth, setTokens
finishLocalSetup, getCustomMessages, getId, getMessageBundle, getSeverity, getSeverityLevel, setId, setSeverity
configure, contextualize, getConfiguration, setupChild
public static final String MSG_KEY
public ThrowsCountCheck()
public int[] getDefaultTokens()
AbstractCheck
getDefaultTokens
in class AbstractCheck
TokenTypes
public int[] getRequiredTokens()
AbstractCheck
getRequiredTokens
in class AbstractCheck
TokenTypes
public int[] getAcceptableTokens()
AbstractCheck
getAcceptableTokens
in class AbstractCheck
TokenTypes
public void setIgnorePrivateMethods(boolean ignorePrivateMethods)
ignorePrivateMethods
- whether private methods must be ignored.public void setMax(int max)
max
- maximum allowed throws statements.public void visitToken(DetailAST ast)
AbstractCheck
visitToken
in class AbstractCheck
ast
- the token to processCopyright © 2001–2020. All rights reserved.