Class BooleanExpressionComplexityCheck
- All Implemented Interfaces:
Configurable
,Contextualizable
Restricts the number of boolean operators (&&
, ||
,
&
, |
and ^
) in an expression.
Rationale: Too many conditions leads to code that is difficult to read and hence debug and maintain.
Note that the operators &
and |
are not only integer bitwise
operators, they are also the
non-shortcut versions of the boolean operators &&
and ||
.
Note that &
, |
and ^
are not checked if they are part
of constructor or method call because they can be applied to non boolean
variables and Checkstyle does not know types of methods from different classes.
-
Property
max
- Specify the maximum number of boolean operations allowed in one expression. Type isint
. Default value is3
. -
Property
tokens
- tokens to check Type isjava.lang.String[]
. Validation type istokenSet
. Default value is: LAND, BAND, LOR, BOR, BXOR.
To configure the check:
<module name="BooleanExpressionComplexity"/>
Code Example:
public class Test { public static void main(String ... args) { boolean a = true; boolean b = false; boolean c = (a & b) | (b ^ a); // OK, 1(&) + 1(|) + 1(^) = 3 (max allowed 3) boolean d = (a & b) ^ (a || b) | a; // violation, 1(&) + 1(^) + 1(||) + 1(|) = 4 } }
To configure the check with 5 allowed operation in boolean expression:
<module name="BooleanExpressionComplexity"> <property name="max" value="5"/> </module>
Code Example:
public class Test { public static void main(String ... args) { boolean a = true; boolean b = false; boolean c = (a & b) | (b ^ a) | (a ^ b); // OK, 1(&) + 1(|) + 1(^) + 1(|) + 1(^) = 5 boolean d = (a | b) ^ (a | b) ^ (a || b) & b; // violation, // 1(|) + 1(^) + 1(|) + 1(^) + 1(||) + 1(&) = 6 } }
To configure the check to ignore &
and |
:
<module name="BooleanExpressionComplexity"> <property name="tokens" value="BXOR,LAND,LOR"/> </module>
Code Example:
public class Test { public static void main(String ... args) { boolean a = true; boolean b = false; boolean c = (!a && b) | (a || !b) ^ a; // OK, 1(&&) + 1(||) + 1(^) = 3 // | is ignored here boolean d = a ^ (a || b) ^ (b || a) & a; // violation, 1(^) + 1(||) + 1(^) + 1(||) = 4 // & is ignored here } }
Parent is com.puppycrawl.tools.checkstyle.TreeWalker
Violation Message Keys:
-
booleanExpressionComplexity
- Since:
- 3.4
-
Nested Class Summary
Nested classes/interfaces inherited from class com.puppycrawl.tools.checkstyle.api.AutomaticBean
AutomaticBean.OutputStreamOptions
-
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
leaveToken
(DetailAST ast) Called after all the child nodes have been process.void
setMax
(int max) Setter to specify the maximum number of boolean operations allowed in one expression.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, 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
-
Field Details
-
MSG_KEY
A key is pointing to the warning message text in "messages.properties" file.- See Also:
-
-
Constructor Details
-
BooleanExpressionComplexityCheck
public BooleanExpressionComplexityCheck()Creates new instance of the check.
-
-
Method Details
-
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:
-
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:
-
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:
-
setMax
public void setMax(int max) Setter to specify the maximum number of boolean operations allowed in one expression.- Parameters:
max
- new maximum allowed complexity.
-
visitToken
Description copied from class:AbstractCheck
Called to process a token.- Overrides:
visitToken
in classAbstractCheck
- Parameters:
ast
- the token to process
-
leaveToken
Description copied from class:AbstractCheck
Called after all the child nodes have been process.- Overrides:
leaveToken
in classAbstractCheck
- Parameters:
ast
- the token leaving
-