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
}
}
Modifier and Type | Field and Description |
---|---|
private int[] |
constantWaiverParentToken
The token types that are allowed in the AST path from the
number literal to the enclosing constant definition.
|
private boolean |
ignoreAnnotation
Whether to ignore magic numbers in annotation.
|
private boolean |
ignoreFieldDeclaration
Whether to ignore magic numbers in field declaration.
|
private boolean |
ignoreHashCodeMethod
Whether to ignore magic numbers in a hash code method.
|
private double[] |
ignoreNumbers
The numbers to ignore in the check, sorted.
|
static java.lang.String |
MSG_KEY
A key is pointing to the warning message text in "messages.properties"
file.
|
Constructor and Description |
---|
MagicNumberCheck()
Constructor for MagicNumber Check.
|
Modifier and Type | Method and Description |
---|---|
private static DetailAST |
findContainingConstantDef(DetailAST ast)
Finds the constant definition that contains aAST.
|
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.
|
private static boolean |
isChildOf(DetailAST ast,
int type)
Determines if the given AST node has a parent node with given token type code.
|
private static boolean |
isFieldDeclaration(DetailAST ast)
Determines whether or not the given AST is field declaration.
|
private static boolean |
isInHashCodeMethod(DetailAST ast)
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 |
reportMagicNumber(DetailAST ast)
Reports aAST as a magic number, includes unary operators as needed.
|
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.
|
beginTree, destroy, finishTree, getClassLoader, getFileContents, getLine, getLines, getTabWidth, getTokenNames, init, isCommentNodesRequired, leaveToken, log, log, setClassLoader, setFileContents, setMessages, setTabWidth, setTokens
getCustomMessages, getId, getMessageBundle, getSeverity, getSeverityLevel, log, setId, setSeverity
configure, contextualize, finishLocalSetup, getConfiguration, setupChild
public static final java.lang.String MSG_KEY
private int[] constantWaiverParentToken
private double[] ignoreNumbers
private boolean ignoreHashCodeMethod
private boolean ignoreAnnotation
private boolean ignoreFieldDeclaration
public MagicNumberCheck()
public int[] getDefaultTokens()
AbstractCheck
getDefaultTokens
in class AbstractCheck
TokenTypes
public int[] getAcceptableTokens()
AbstractCheck
getAcceptableTokens
in class AbstractCheck
TokenTypes
public int[] getRequiredTokens()
AbstractCheck
getRequiredTokens
in class AbstractCheck
TokenTypes
public void visitToken(DetailAST ast)
AbstractCheck
visitToken
in class AbstractCheck
ast
- the token to processprivate boolean isMagicNumberExists(DetailAST ast, DetailAST constantDefAST)
ast
- ast tokenconstantDefAST
- constant astprivate static DetailAST findContainingConstantDef(DetailAST ast)
ast
- the ASTprivate void reportMagicNumber(DetailAST ast)
ast
- the AST node that contains the number to reportprivate static boolean isInHashCodeMethod(DetailAST ast)
public int hashCode()
.ast
- the AST from which to search for an enclosing hash code
method definitiontrue
if ast
is in the scope of a valid hash code method.private boolean isInIgnoreList(DetailAST ast)
ast
- the AST to checkprivate static boolean isFieldDeclaration(DetailAST ast)
ast
- AST from which to search for an enclosing field declarationtrue
if ast
is in the scope of field declarationpublic void setConstantWaiverParentToken(java.lang.String... tokens)
tokens
- The string representation of the tokens interested inpublic void setIgnoreNumbers(double... list)
list
- list of numbers to ignore.public void setIgnoreHashCodeMethod(boolean ignoreHashCodeMethod)
ignoreHashCodeMethod
- decide whether to ignore
hash code methodspublic void setIgnoreAnnotation(boolean ignoreAnnotation)
ignoreAnnotation
- decide whether to ignore annotationspublic void setIgnoreFieldDeclaration(boolean ignoreFieldDeclaration)
ignoreFieldDeclaration
- decide whether to ignore magic numbers
in field declarationprivate static boolean isChildOf(DetailAST ast, int type)
ast
- the AST from which to search for annotationstype
- the type code of parent tokentrue
if the AST node has a parent with given token type.