Class ClassFanOutComplexityCheck
- All Implemented Interfaces:
Configurable
,Contextualizable
Checks the number of other types a given class/record/interface/enum/annotation relies on. Also the square of this has been shown to indicate the amount of maintenance required in functional programs (on a file basis) at least.
This check processes files in the following way:
- Iterates over all tokens that might contain type reference.
-
If a class was imported with direct import (i.e.
import java.math.BigDecimal
), or the class was referenced with the package name (i.e.java.math.BigDecimal value
) and the package was added to theexcludedPackages
parameter, the class does not increase complexity. -
If a class name was added to the
excludedClasses
parameter, the class does not increase complexity.
-
Property
max
- Specify the maximum threshold allowed. Type isint
. Default value is20
. -
Property
excludedClasses
- Specify user-configured class names to ignore. Type isjava.lang.String[]
. Default value isArrayIndexOutOfBoundsException, ArrayList, Boolean, Byte, Character, Class, Deprecated, Deque, Double, Exception, Float, FunctionalInterface, HashMap, HashSet, IllegalArgumentException, IllegalStateException, IndexOutOfBoundsException, Integer, LinkedList, List, Long, Map, NullPointerException, Object, Override, Queue, RuntimeException, SafeVarargs, SecurityException, Set, Short, SortedMap, SortedSet, String, StringBuffer, StringBuilder, SuppressWarnings, Throwable, TreeMap, TreeSet, UnsupportedOperationException, Void, boolean, byte, char, double, float, int, long, short, void
. -
Property
excludeClassesRegexps
- Specify user-configured regular expressions to ignore classes. Type isjava.lang.String[]
. Validation type isjava.util.regex.Pattern
. Default value is^$
. -
Property
excludedPackages
- Specify user-configured packages to ignore. All excluded packages should end with a period, so it also appends a dot to a package name. Type isjava.lang.String[]
. Default value is""
.
To configure the check:
<module name="ClassFanOutComplexity"/>
Example:
The check passes without violations in the following:
class InputClassComplexity { Set set = new HashSet(); // Set, HashSet ignored due to default excludedClasses property Map map = new HashMap(); // Map, HashMap ignored due to default excludedClasses property Date date = new Date(); // Counted, 1 Time time = new Time(); // Counted, 2 Place place = new Place(); // Counted, 3 }
The check results in a violation in the following:
class InputClassComplexity { Set set = new HashSet(); // Set, HashSet ignored due to default excludedClasses property Map map = new HashMap(); // Map, HashMap ignored due to default excludedClasses property Date date = new Date(); // Counted, 1 Time time = new Time(); // Counted, 2 // mention of 18 other user defined classes Place place = new Place(); // violation, total is 21 }
To configure the check with a threshold of 2:
<module name="ClassFanOutComplexity"> <property name="max" value="2"/> </module>
Example:
The check passes without violations in the following:
class InputClassComplexity { Set set = new HashSet(); // Set, HashSet ignored due to default excludedClasses property Map map = new HashMap(); // Map, HashMap ignored due to default excludedClasses property Date date = new Date(); // Counted, 1 Time time = new Time(); // Counted, 2 }
The check results in a violation in the following:
class InputClassComplexity { Set set = new HashSet(); // Set, HashSet ignored due to default excludedClasses property Map map = new HashMap(); // Map, HashMap ignored due to default excludedClasses property Date date = new Date(); // Counted, 1 Time time = new Time(); // Counted, 2 Place place = new Place(); // violation, total is 3 }
To configure the check with three excluded classes HashMap
,
HashSet
and Place
:
<module name="ClassFanOutComplexity"> <property name="excludedClasses" value="HashMap, HashSet, Place"/> </module>
Example:
The check passes without violations in the following:
class InputClassComplexity { Set set = new HashSet(); // Set counted 1, HashSet ignored Map map = new HashMap(); // Map counted 2, HashMap ignored Date date = new Date(); // Counted, 3 Time time = new Time(); // Counted, 4 // mention of 16 other user defined classes Place place = new Place(); // Ignored }
The check results in a violation in the following:
class InputClassComplexity { Set set = new HashSet(); // Set counted 1, HashSet ignored Map map = new HashMap(); // Map counted 2, HashMap ignored Date date = new Date(); // Counted, 3 Time time = new Time(); // Counted, 4 // mention of 16 other user defined classes Space space = new Space(); // violation, total is 21 }
To configure the check to exclude classes with a regular expression
.*Reader$
:
<module name="ClassFanOutComplexity"> <property name="excludeClassesRegexps" value=".*Reader$"/> </module>
Example:
The check passes without violations in the following:
class InputClassComplexity { Set set = new HashSet(); // Set, HashSet ignored due to default excludedClasses property Map map = new HashMap(); // Map, HashMap ignored due to default excludedClasses property Date date = new Date(); // Counted, 1 Time time = new Time(); // Counted, 2 // mention of 18 other user defined classes BufferedReader br; // Ignored }
The check results in a violation in the following:
class InputClassComplexity { Set set = new HashSet(); // Set, HashSet ignored due to default excludedClasses property Map map = new HashMap(); // Map, HashMap ignored due to default excludedClasses property Date date = new Date(); // Counted, 1 Time time = new Time(); // Counted, 2 // mention of 18 other user defined classes File file; // violation, total is 21 }
To configure the check with an excluded package java.io
:
<module name="ClassFanOutComplexity"> <property name="excludedPackages" value="java.io"/> </module>
Example:
The check passes without violations in the following:
import java.io.BufferedReader; class InputClassComplexity { Set set = new HashSet(); // Set, HashSet ignored due to default excludedClasses property Map map = new HashMap(); // Map, HashMap ignored due to default excludedClasses property Date date = new Date(); // Counted, 1 Time time = new Time(); // Counted, 2 // mention of 18 other user defined classes BufferedReader br; // Ignored }
The check results in a violation in the following:
import java.util.StringTokenizer; class InputClassComplexity { Set set = new HashSet(); // Set, HashSet ignored due to default excludedClasses property Map map = new HashMap(); // Map, HashMap ignored due to default excludedClasses property Date date = new Date(); // Counted, 1 Time time = new Time(); // Counted, 2 // mention of 18 other user defined classes StringTokenizer st; // violation, total is 21 }
Override property excludedPackages
to mark some packages as excluded.
Each member of excludedPackages
should be a valid identifier:
-
java.util
- valid, excludes all classes insidejava.util
, but not from the subpackages. -
java.util.
- invalid, should not end with a dot. -
java.util.*
- invalid, should not end with a star.
Note, that checkstyle will ignore all classes from the java.lang
package and its subpackages, even if the java.lang
was not listed
in the excludedPackages
parameter.
Also note, that excludedPackages
will not exclude classes, imported
via wildcard (e.g. import java.math.*
). Instead of wildcard import
you should use direct import (e.g. import java.math.BigDecimal
).
Also note, that checkstyle will not exclude classes within the same file even
if it was listed in the excludedPackages
parameter.
For example, assuming the config is
<module name="ClassFanOutComplexity"> <property name="excludedPackages" value="a.b"/> </module>
And the file a.b.Foo.java
is:
package a.b; import a.b.Bar; import a.b.c.Baz; class Foo { Bar bar; // Will be ignored, located inside ignored a.b package Baz baz; // Will not be ignored, located inside a.b.c package Data data; // Will not be ignored, same file class Data { Foo foo; // Will not be ignored, same file } }
The bar
member will not be counted, since the a.b
added to the excludedPackages
. The baz
member will be counted,
since the a.b.c
was not added to the excludedPackages
.
The data
and foo
members will be counted, as they are inside same file.
Parent is com.puppycrawl.tools.checkstyle.TreeWalker
Violation Message Keys:
-
classFanOutComplexity
- Since:
- 3.4
-
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.protected String
Returns message key we use for log violations.int[]
The tokens that this check must be registered for.Methods inherited from class com.puppycrawl.tools.checkstyle.checks.metrics.AbstractClassCouplingCheck
beginTree, getDefaultTokens, leaveToken, setExcludeClassesRegexps, setExcludedClasses, setExcludedPackages, setMax, visitToken
Methods inherited from class com.puppycrawl.tools.checkstyle.api.AbstractCheck
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
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Field Details
-
MSG_KEY
A key is pointing to the warning message text in "messages.properties" file.- See Also:
-
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Constructor Details
-
ClassFanOutComplexityCheck
public ClassFanOutComplexityCheck()Creates new instance of this check.
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Method Details
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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:
-
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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getLogMessageId
Description copied from class:AbstractClassCouplingCheck
Returns message key we use for log violations.- Specified by:
getLogMessageId
in classAbstractClassCouplingCheck
- Returns:
- message key we use for log violations.
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