Class MagicNumberCheck
- java.lang.Object
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- com.puppycrawl.tools.checkstyle.api.AutomaticBean
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- com.puppycrawl.tools.checkstyle.api.AbstractViolationReporter
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- com.puppycrawl.tools.checkstyle.api.AbstractCheck
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- com.puppycrawl.tools.checkstyle.checks.coding.MagicNumberCheck
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- All Implemented Interfaces:
Configurable
,Contextualizable
public class MagicNumberCheck extends AbstractCheck
Checks that there are no "magic numbers" where a magic number is a numeric literal that is not defined as a constant. By default, -1, 0, 1, and 2 are not considered to be magic numbers.
Constant definition is any variable/field that has 'final' modifier. It is fine to have one constant defining multiple numeric literals within one expression:
static final int SECONDS_PER_DAY = 24 * 60 * 60; static final double SPECIAL_RATIO = 4.0 / 3.0; static final double SPECIAL_SUM = 1 + Math.E; static final double SPECIAL_DIFFERENCE = 4 - Math.PI; static final Border STANDARD_BORDER = BorderFactory.createEmptyBorder(3, 3, 3, 3); static final Integer ANSWER_TO_THE_ULTIMATE_QUESTION_OF_LIFE = new Integer(42);
Check have following options: ignoreHashCodeMethod - ignore magic numbers in hashCode methods; ignoreAnnotation - ignore magic numbers in annotation declarations; ignoreFieldDeclaration - ignore magic numbers in field declarations.
To configure the check with default configuration:
<module name="MagicNumber"/>
results is following violations:
{@literal @}MyAnnotation(6) // violation class MyClass { private field = 7; // violation void foo() { int i = i + 1; // no violation int j = j + 8; // violation } }
To configure the check so that it checks floating-point numbers that are not 0, 0.5, or 1:
<module name="MagicNumber"> <property name="tokens" value="NUM_DOUBLE, NUM_FLOAT"/> <property name="ignoreNumbers" value="0, 0.5, 1"/> <property name="ignoreFieldDeclaration" value="true"/> <property name="ignoreAnnotation" value="true"/> </module>
results is following violations:
{@literal @}MyAnnotation(6) // no violation class MyClass { private field = 7; // no violation void foo() { int i = i + 1; // no violation int j = j + (int)0.5; // no violation } }
Config example of constantWaiverParentToken option:
<module name="MagicNumber"> <property name="constantWaiverParentToken" value="ASSIGN,ARRAY_INIT,EXPR, UNARY_PLUS, UNARY_MINUS, TYPECAST, ELIST, DIV, PLUS "/> </module>
result is following violation:
class TestMethodCall { public void method2() { final TestMethodCall dummyObject = new TestMethodCall(62); //violation final int a = 3; // ok as waiver is ASSIGN final int [] b = {4, 5} // ok as waiver is ARRAY_INIT final int c = -3; // ok as waiver is UNARY_MINUS final int d = +4; // ok as waiver is UNARY_PLUS final int e = method(1, 2) // ELIST is there but violation due to METHOD_CALL final int x = 3 * 4; // violation final int y = 3 / 4; // ok as waiver is DIV final int z = 3 + 4; // ok as waiver is PLUS final int w = 3 - 4; // violation final int x = (int)(3.4); //ok as waiver is TYPECAST } }
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Nested Class Summary
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Nested classes/interfaces inherited from class com.puppycrawl.tools.checkstyle.api.AutomaticBean
AutomaticBean.OutputStreamOptions
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Field Summary
Fields Modifier and Type Field Description static java.lang.String
MSG_KEY
A key is pointing to the warning message text in "messages.properties" file.
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Constructor Summary
Constructors Constructor Description MagicNumberCheck()
Constructor for MagicNumber Check.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method 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
setConstantWaiverParentToken(java.lang.String... tokens)
Sets the tokens which are allowed between Magic Number and defined Object.void
setIgnoreAnnotation(boolean ignoreAnnotation)
Set whether to ignore Annotations.void
setIgnoreFieldDeclaration(boolean ignoreFieldDeclaration)
Set whether to ignore magic numbers in field declaration.void
setIgnoreHashCodeMethod(boolean ignoreHashCodeMethod)
Set whether to ignore hashCode methods.void
setIgnoreNumbers(double... list)
Sets the numbers to ignore in the check.void
visitToken(DetailAST ast)
Called to process a token.-
Methods inherited from class com.puppycrawl.tools.checkstyle.api.AbstractCheck
beginTree, clearMessages, destroy, finishTree, getClassLoader, getFileContents, getLine, getLines, getMessages, getTabWidth, getTokenNames, init, isCommentNodesRequired, leaveToken, log, log, log, setClassLoader, setFileContents, setTabWidth, setTokens
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Methods inherited from class com.puppycrawl.tools.checkstyle.api.AbstractViolationReporter
finishLocalSetup, getCustomMessages, getId, getMessageBundle, getSeverity, getSeverityLevel, setId, setSeverity
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Methods inherited from class com.puppycrawl.tools.checkstyle.api.AutomaticBean
configure, contextualize, getConfiguration, setupChild
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Field Detail
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MSG_KEY
public static final java.lang.String MSG_KEY
A key is pointing to the warning message text in "messages.properties" file.- See Also:
- Constant Field Values
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Method Detail
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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:
TokenTypes
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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:
TokenTypes
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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:
TokenTypes
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visitToken
public void visitToken(DetailAST ast)
Description copied from class:AbstractCheck
Called to process a token.- Overrides:
visitToken
in classAbstractCheck
- Parameters:
ast
- the token to process
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setConstantWaiverParentToken
public void setConstantWaiverParentToken(java.lang.String... tokens)
Sets the tokens which are allowed between Magic Number and defined Object.- Parameters:
tokens
- The string representation of the tokens interested in
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setIgnoreNumbers
public void setIgnoreNumbers(double... list)
Sets the numbers to ignore in the check. BeanUtils converts numeric token list to double array automatically.- Parameters:
list
- list of numbers to ignore.
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setIgnoreHashCodeMethod
public void setIgnoreHashCodeMethod(boolean ignoreHashCodeMethod)
Set whether to ignore hashCode methods.- Parameters:
ignoreHashCodeMethod
- decide whether to ignore hash code methods
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setIgnoreAnnotation
public void setIgnoreAnnotation(boolean ignoreAnnotation)
Set whether to ignore Annotations.- Parameters:
ignoreAnnotation
- decide whether to ignore annotations
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setIgnoreFieldDeclaration
public void setIgnoreFieldDeclaration(boolean ignoreFieldDeclaration)
Set whether to ignore magic numbers in field declaration.- Parameters:
ignoreFieldDeclaration
- decide whether to ignore magic numbers in field declaration
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