Package com.puppycrawl.tools.checkstyle.checks.coding

Class MagicNumberCheck

java.lang.Object
com.puppycrawl.tools.checkstyle.AbstractAutomaticBean
com.puppycrawl.tools.checkstyle.api.AbstractViolationReporter
com.puppycrawl.tools.checkstyle.api.AbstractCheck
com.puppycrawl.tools.checkstyle.checks.coding.MagicNumberCheck
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);
  • Property constantWaiverParentToken - Specify tokens that are allowed in the AST path from the number literal to the enclosing constant definition. Type is java.lang.String[]. Validation type is tokenTypesSet. Default value is ARRAY_INIT, ASSIGN, BAND, BNOT, BOR, BSR, BXOR, COLON, DIV, ELIST, EQUAL, EXPR, GE, GT, LE, LITERAL_NEW, LT, METHOD_CALL, MINUS, MOD, NOT_EQUAL, PLUS, QUESTION, SL, SR, STAR, TYPECAST, UNARY_MINUS, UNARY_PLUS.
  • Property ignoreAnnotation - Ignore magic numbers in annotation declarations. Type is boolean. Default value is false.
  • Property ignoreAnnotationElementDefaults - Ignore magic numbers in annotation elements defaults. Type is boolean. Default value is true.
  • Property ignoreFieldDeclaration - Ignore magic numbers in field declarations. Type is boolean. Default value is false.
  • Property ignoreHashCodeMethod - Ignore magic numbers in hashCode methods. Type is boolean. Default value is false.
  • Property ignoreNumbers - Specify non-magic numbers. Type is double[]. Default value is -1, 0, 1, 2.
  • Property tokens - tokens to check Type is java.lang.String[]. Validation type is tokenSet. Default value is: NUM_DOUBLE, NUM_FLOAT, NUM_INT, NUM_LONG.

Parent is com.puppycrawl.tools.checkstyle.TreeWalker

Violation Message Keys:

  • magic.number
Since:
3.1

  • Field Details

    • MSG_KEY

      public static final String MSG_KEY
      A key is pointing to the warning message text in "messages.properties" file.
      See Also:

    • constantWaiverParentToken

      private BitSet constantWaiverParentToken
      Specify tokens that are allowed in the AST path from the number literal to the enclosing constant definition.

    • ignoreNumbers

      private double[] ignoreNumbers
      Specify non-magic numbers.

    • ignoreHashCodeMethod

      private boolean ignoreHashCodeMethod
      Ignore magic numbers in hashCode methods.

    • ignoreAnnotation

      private boolean ignoreAnnotation
      Ignore magic numbers in annotation declarations.

    • ignoreFieldDeclaration

      private boolean ignoreFieldDeclaration
      Ignore magic numbers in field declarations.

    • ignoreAnnotationElementDefaults

      private boolean ignoreAnnotationElementDefaults
      Ignore magic numbers in annotation elements defaults.

  • Constructor Details

  • 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 class AbstractCheck
      Returns:
      the default tokens
      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 class AbstractCheck
      Returns:
      the token set this check is designed for.
      See Also:

    • getRequiredTokens

      public int[] getRequiredTokens()
      Description copied from class: AbstractCheck
      The tokens that this check must be registered for.
      Specified by:
      getRequiredTokens in class AbstractCheck
      Returns:
      the token set this must be registered for.
      See Also:

    • visitToken

      public void visitToken(DetailAST ast)
      Description copied from class: AbstractCheck
      Called to process a token.
      Overrides:
      visitToken in class AbstractCheck
      Parameters:
      ast - the token to process

    • shouldTestAnnotationArgs

      private boolean shouldTestAnnotationArgs(DetailAST ast)
      Checks if ast is annotation argument and should be checked.
      Parameters:
      ast - token to check
      Returns:
      true if element is skipped, false otherwise

    • shouldTestAnnotationDefaults

      private boolean shouldTestAnnotationDefaults(DetailAST ast)
      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

    • shouldCheckHashCodeMethod

      private boolean shouldCheckHashCodeMethod(DetailAST ast)
      Checks if the given AST node is a HashCode Method and should be checked.
      Parameters:
      ast - the AST node to check
      Returns:
      true if element should be checked, false otherwise

    • shouldCheckFieldDeclaration

      private boolean shouldCheckFieldDeclaration(DetailAST ast)
      Checks if the given AST node is a field declaration and should be checked.
      Parameters:
      ast - the AST node to check
      Returns:
      true if element should be checked, false otherwise

    • isMagicNumberExists

      private boolean isMagicNumberExists(DetailAST ast, DetailAST constantDefAST)
      Is magic number somewhere at ast tree.
      Parameters:
      ast - ast token
      constantDefAST - constant ast
      Returns:
      true if magic number is present

    • findContainingConstantDef

      private static DetailAST findContainingConstantDef(DetailAST ast)
      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.

    • reportMagicNumber

      private void reportMagicNumber(DetailAST ast)
      Reports aAST as a magic number, includes unary operators as needed.
      Parameters:
      ast - the AST node that contains the number to report

    • isInHashCodeMethod

      private static boolean isInHashCodeMethod(DetailAST ast)
      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 signature public int hashCode().
      Parameters:
      ast - the AST from which to search for an enclosing hash code method definition
      Returns:
      true if ast is in the scope of a valid hash code method.

    • isInIgnoreList

      private boolean isInIgnoreList(DetailAST ast)
      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.

    • isFieldDeclaration

      private static boolean isFieldDeclaration(DetailAST ast)
      Determines whether or not the given AST is field declaration.
      Parameters:
      ast - AST from which to search for an enclosing field declaration
      Returns:
      true if ast is in the scope of field declaration

    • setConstantWaiverParentToken

      public void setConstantWaiverParentToken(String... tokens)
      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
      Since:
      6.11

    • setIgnoreNumbers

      public void setIgnoreNumbers(double... list)
      Setter to specify non-magic numbers.
      Parameters:
      list - numbers to ignore.
      Since:
      3.1

    • setIgnoreHashCodeMethod

      public void setIgnoreHashCodeMethod(boolean ignoreHashCodeMethod)
      Setter to ignore magic numbers in hashCode methods.
      Parameters:
      ignoreHashCodeMethod - decide whether to ignore hash code methods
      Since:
      5.3

    • setIgnoreAnnotation

      public void setIgnoreAnnotation(boolean ignoreAnnotation)
      Setter to ignore magic numbers in annotation declarations.
      Parameters:
      ignoreAnnotation - decide whether to ignore annotations
      Since:
      5.4

    • 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
      Since:
      6.6

    • setIgnoreAnnotationElementDefaults

      public void setIgnoreAnnotationElementDefaults(boolean ignoreAnnotationElementDefaults)
      Setter to ignore magic numbers in annotation elements defaults.
      Parameters:
      ignoreAnnotationElementDefaults - decide whether to ignore annotation elements defaults
      Since:
      8.23

    • isChildOf

      private static boolean isChildOf(DetailAST ast, int type)
      Determines if the given AST node has a parent node with given token type code.
      Parameters:
      ast - the AST from which to search for annotations
      type - the type code of parent token
      Returns:
      true if the AST node has a parent with given token type.