Class MagicNumberCheck
- All Implemented Interfaces:
Configurable
,Contextualizable
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);
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Property
ignoreNumbers
- Specify non-magic numbers. Type isdouble[]
. Default value is-1, 0, 1, 2
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Property
ignoreHashCodeMethod
- Ignore magic numbers in hashCode methods. Type isboolean
. Default value isfalse
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Property
ignoreAnnotation
- Ignore magic numbers in annotation declarations. Type isboolean
. Default value isfalse
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Property
ignoreFieldDeclaration
- Ignore magic numbers in field declarations. Type isboolean
. Default value isfalse
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Property
ignoreAnnotationElementDefaults
- Ignore magic numbers in annotation elements defaults. Type isboolean
. Default value istrue
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Property
constantWaiverParentToken
- Specify tokens that are allowed in the AST path from the number literal to the enclosing constant definition. Type isjava.lang.String[]
. Validation type istokenTypesSet
. Default value is TYPECAST, METHOD_CALL, EXPR, ARRAY_INIT, UNARY_MINUS, UNARY_PLUS, ELIST, STAR, ASSIGN, PLUS, MINUS, DIV, LITERAL_NEW. -
Property
tokens
- tokens to check Type isjava.lang.String[]
. Validation type istokenSet
. Default value is: NUM_DOUBLE, NUM_FLOAT, NUM_INT, NUM_LONG.
To configure the check with default configuration:
<module name="MagicNumber"/>
results is following violations:
@MyAnnotation(6) // violation class MyClass { private field = 7; // violation void foo() { int i = i + 1; // no violation int j = j + 8; // violation } public int hashCode() { return 10; // violation } } @interface anno { int value() default 10; // no 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:
@MyAnnotation(6) // no violation class MyClass { private field = 7; // no violation void foo() { int i = i + 1; // no violation int j = j + 8; // violation } }
To configure the check so that it ignores magic numbers in field declarations:
<module name="MagicNumber"> <property name="ignoreFieldDeclaration" value="false"/> </module>
results in the following violations:
public record MyRecord() { private static int myInt = 7; // ok, field declaration void foo() { int i = myInt + 1; // no violation, 1 is defined as non-magic int j = myInt + 8; // violation } }
To configure the check to check annotation element defaults:
<module name="MagicNumber"> <property name="ignoreAnnotationElementDefaults" value="false"/> </module>
results in following violations:
@interface anno { int value() default 10; // violation int[] value2() default {10}; // 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 } }
Config example of ignoreHashCodeMethod option:
<module name="MagicNumber"> <property name="ignoreHashCodeMethod" value="true"/> </module>
result is no violation:
class TestHashCode { public int hashCode() { return 10; // OK } }
Parent is com.puppycrawl.tools.checkstyle.TreeWalker
Violation Message Keys:
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magic.number
- Since:
- 3.1
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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
FieldsModifier and TypeFieldDescriptionprivate int[]
Specify tokens that are allowed in the AST path from the number literal to the enclosing constant definition.private boolean
Ignore magic numbers in annotation declarations.private boolean
Ignore magic numbers in annotation elements defaults.private boolean
Ignore magic numbers in field declarations.private boolean
Ignore magic numbers in hashCode methods.private double[]
Specify non-magic numbers.static final String
A key is pointing to the warning message text in "messages.properties" file. -
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionprivate static DetailAST
Finds the constant definition that contains aAST.int[]
The configurable token set.int[]
Returns the default token a check is interested in.int[]
The tokens that this check must be registered for.private static boolean
Determines if the given AST node has a parent node with given token type code.private static boolean
Determines whether or not the given AST is field declaration.private static boolean
Determines whether or not the given AST is in a valid hash code method.private boolean
isInIgnoreList
(DetailAST ast) Decides whether the number of an AST is in the ignore list of this check.private boolean
isMagicNumberExists
(DetailAST ast, DetailAST constantDefAST) Is magic number some where at ast tree.private void
Reports aAST as a magic number, includes unary operators as needed.void
setConstantWaiverParentToken
(String... tokens) Setter to specify tokens that are allowed in the AST path from the number literal to the enclosing constant definition.void
setIgnoreAnnotation
(boolean ignoreAnnotation) Setter to ignore magic numbers in annotation declarations.void
setIgnoreAnnotationElementDefaults
(boolean ignoreAnnotationElementDefaults) Setter to ignore magic numbers in annotation elements defaults.void
setIgnoreFieldDeclaration
(boolean ignoreFieldDeclaration) Setter to ignore magic numbers in field declarations.void
setIgnoreHashCodeMethod
(boolean ignoreHashCodeMethod) Setter to ignore magic numbers in hashCode methods.void
setIgnoreNumbers
(double... list) Setter to specify non-magic numbers.private boolean
Checks if ast is annotation argument and should be checked.private boolean
Checks if ast is annotation element default value and should be checked.void
visitToken
(DetailAST ast) Called to process a token.Methods inherited from class com.puppycrawl.tools.checkstyle.api.AbstractCheck
beginTree, clearViolations, destroy, finishTree, getFileContents, getLine, getLineCodePoints, getLines, getTabWidth, getTokenNames, getViolations, 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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constantWaiverParentToken
private int[] constantWaiverParentTokenSpecify tokens that are allowed in the AST path from the number literal to the enclosing constant definition. -
ignoreNumbers
private double[] ignoreNumbersSpecify non-magic numbers. -
ignoreHashCodeMethod
private boolean ignoreHashCodeMethodIgnore magic numbers in hashCode methods. -
ignoreAnnotation
private boolean ignoreAnnotationIgnore magic numbers in annotation declarations. -
ignoreFieldDeclaration
private boolean ignoreFieldDeclarationIgnore magic numbers in field declarations. -
ignoreAnnotationElementDefaults
private boolean ignoreAnnotationElementDefaultsIgnore magic numbers in annotation elements defaults.
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Constructor Details
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MagicNumberCheck
public MagicNumberCheck()Constructor for MagicNumber Check. Sort the allowedTokensBetweenMagicNumberAndConstDef array for binary search.
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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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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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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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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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shouldTestAnnotationArgs
Checks if ast is annotation argument and should be checked.- Parameters:
ast
- token to check- Returns:
- true if element is skipped, false otherwise
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shouldTestAnnotationDefaults
Checks if ast is annotation element default value and should be checked.- Parameters:
ast
- token to check- Returns:
- true if element is skipped, false otherwise
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isMagicNumberExists
Is magic number some where at ast tree.- Parameters:
ast
- ast tokenconstantDefAST
- constant ast- Returns:
- true if magic number is present
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findContainingConstantDef
Finds the constant definition that contains aAST.- Parameters:
ast
- the AST- Returns:
- the constant def or null if ast is not contained in a constant definition.
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reportMagicNumber
Reports aAST as a magic number, includes unary operators as needed.- Parameters:
ast
- the AST node that contains the number to report
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isInHashCodeMethod
Determines whether or not the given AST is in a valid hash code method. A valid hash code method is considered to be a method of the signaturepublic int hashCode()
.- Parameters:
ast
- the AST from which to search for an enclosing hash code method definition- Returns:
true
ifast
is in the scope of a valid hash code method.
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isInIgnoreList
Decides whether the number of an AST is in the ignore list of this check.- Parameters:
ast
- the AST to check- Returns:
- true if the number of ast is in the ignore list of this check.
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isFieldDeclaration
Determines whether or not the given AST is field declaration.- Parameters:
ast
- AST from which to search for an enclosing field declaration- Returns:
true
ifast
is in the scope of field declaration
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setConstantWaiverParentToken
Setter to specify tokens that are allowed in the AST path from the number literal to the enclosing constant definition.- Parameters:
tokens
- The string representation of the tokens interested in
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setIgnoreNumbers
public void setIgnoreNumbers(double... list) Setter to specify non-magic numbers.- Parameters:
list
- list of numbers to ignore.
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setIgnoreHashCodeMethod
public void setIgnoreHashCodeMethod(boolean ignoreHashCodeMethod) Setter to ignore magic numbers in hashCode methods.- Parameters:
ignoreHashCodeMethod
- decide whether to ignore hash code methods
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setIgnoreAnnotation
public void setIgnoreAnnotation(boolean ignoreAnnotation) Setter to ignore magic numbers in annotation declarations.- Parameters:
ignoreAnnotation
- decide whether to ignore annotations
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setIgnoreFieldDeclaration
public void setIgnoreFieldDeclaration(boolean ignoreFieldDeclaration) Setter to ignore magic numbers in field declarations.- Parameters:
ignoreFieldDeclaration
- decide whether to ignore magic numbers in field declaration
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setIgnoreAnnotationElementDefaults
public void setIgnoreAnnotationElementDefaults(boolean ignoreAnnotationElementDefaults) Setter to ignore magic numbers in annotation elements defaults.- Parameters:
ignoreAnnotationElementDefaults
- decide whether to ignore annotation elements defaults
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isChildOf
Determines if the given AST node has a parent node with given token type code.- Parameters:
ast
- the AST from which to search for annotationstype
- the type code of parent token- Returns:
true
if the AST node has a parent with given token type.
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