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

Class IllegalSymbolCheck

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.IllegalSymbolCheck

All Implemented Interfaces:

Configurable, Contextualizable

public class IllegalSymbolCheck
extends AbstractCheck

Checks that specified symbols (by Unicode code points or ranges) are not used in code. By default, blocks common symbol ranges.

Rationale: This check helps prevent emoji symbols and special characters in code (commonly added by AI tools), enforce coding standards, or forbid specific Unicode characters.

Default ranges cover:

• U+2190–U+27BF: Arrows, Mathematical Operators, Box Drawing, Geometric Shapes, Miscellaneous Symbols, and Dingbats
• U+1F600–U+1F64F: Emoticons
• U+1F680–U+1F6FF: Transport and Map Symbols
• U+1F700–U+10FFFF: Alchemical Symbols and other pictographic symbols

For a complete list of Unicode characters and ranges, see: List of Unicode characters

• Property symbolCodes - Specify the symbols to check for, as Unicode code points or ranges. Format: comma-separated list of hex codes or ranges (e.g., "0x2705, 0x1F600-0x1F64F"). To allow only ASCII characters, use "0x0080-0x10FFFF". Type is java.lang.String. Default value is "0x2190-0x27BF, 0x1F600-0x1F64F, 0x1F680-0x1F6FF, 0x1F700-0x10FFFF".

Since:

13.4.0

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private static final record	IllegalSymbolCheck.CodePointRange	Represents a Unicode code point range.

Nested classes/interfaces inherited from class com.puppycrawl.tools.checkstyle.AbstractAutomaticBean

AbstractAutomaticBean.OutputStreamOptions

Field Summary

Fields

Modifier and Type	Field	Description
private final Set<IllegalSymbolCheck.CodePointRange>	codePointRanges	Set of Unicode ranges to disallow.
private static final String	DEFAULT_ILLEGAL_CODES	Default symbol codes to check for.
static final String	MSG_KEY	A key is pointing to the warning message text in "messages.properties" file.
private static final String	RANGE_SEPARATOR	Separator used for defining ranges.
private final Set<Integer>	singleCodePoints	Set of individual Unicode code points to disallow.
private String	symbolCodes	Specify the symbols to check for, as Unicode code points or ranges.

Constructor Summary

Constructors

Constructor	Description
IllegalSymbolCheck()

Method Summary

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	init()	Initializes the check after all properties are set.
boolean	isCommentNodesRequired()	Whether comment nodes are required or not.
private boolean	isIllegalSymbol(int codePoint)	Determines whether a code point is illegal.
private static int	parseCodePoint(String str)	Parses a Unicode code point from a trimmed string.
private void	parseRange(String rangeStr)	Parses and stores a Unicode range.
private void	parseSymbolCodes()	Parses the configured symbolCodes string into singleCodePoints and codePointRanges.
void	setSymbolCodes(String symbols)	Setter to specify the symbols to check for.
void	visitToken(DetailAST ast)	Called to process a token.

Methods inherited from class com.puppycrawl.tools.checkstyle.api.AbstractCheck

beginTree, clearViolations, destroy, finishTree, getFileContents, getFilePath, getLine, getLineCodePoints, getLines, getTabWidth, getTokenNames, getViolations, 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.AbstractAutomaticBean

configure, contextualize, getConfiguration, setupChild

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

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:

• Constant Field Values

RANGE_SEPARATOR

private static final String RANGE_SEPARATOR

Separator used for defining ranges.

See Also:

• Constant Field Values

DEFAULT_ILLEGAL_CODES

private static final String DEFAULT_ILLEGAL_CODES

Default symbol codes to check for.

See Also:

• Constant Field Values

singleCodePoints

private final Set<Integer> singleCodePoints

Set of individual Unicode code points to disallow.

codePointRanges

private final Set<IllegalSymbolCheck.CodePointRange> codePointRanges

Set of Unicode ranges to disallow.

symbolCodes

private String symbolCodes

Specify the symbols to check for, as Unicode code points or ranges.

Constructor Details

IllegalSymbolCheck

public IllegalSymbolCheck()

Method Details

setSymbolCodes

public void setSymbolCodes(String symbols)

Setter to specify the symbols to check for.

Parameters:

symbols - the symbols specification

Throws:

IllegalArgumentException - if the format is invalid

Since:

13.4.0

init

public void init()

Initializes the check after all properties are set.

Ensures that the symbolCodes property is parsed for both default configuration and custom user configuration.

Overrides:

init in class AbstractCheck

Throws:

IllegalArgumentException - if the configured symbol format is invalid

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:

• TokenTypes

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:

• TokenTypes

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:

• TokenTypes

isCommentNodesRequired

public boolean isCommentNodesRequired()

Description copied from class: AbstractCheck

Whether comment nodes are required or not.

Overrides:

isCommentNodesRequired in class AbstractCheck

Returns:

false as a default value.

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

parseSymbolCodes

private void parseSymbolCodes()

Parses the configured symbolCodes string into singleCodePoints and codePointRanges.

Throws:

IllegalArgumentException - if format is invalid

isIllegalSymbol

private boolean isIllegalSymbol(int codePoint)

Determines whether a code point is illegal.

Parameters:

codePoint - Unicode code point

Returns:

true if illegal; false otherwise

parseRange

private void parseRange(String rangeStr)

Parses and stores a Unicode range.

Parameters:

rangeStr - range definition string (already trimmed by caller)

Throws:

IllegalArgumentException - if format is invalid

parseCodePoint

private static int parseCodePoint(String str)

Parses a Unicode code point from a trimmed string. Supported formats: 0x1234, \\u1234, U+1234, or plain hex.

Parameters:

str - input string (already trimmed by caller)

Returns:

parsed code point

Throws:

NumberFormatException - if invalid format