com.github.sevntu.checkstyle.checks.coding

Class NumericLiteralNeedsUnderscoreCheck

java.lang.Object

com.puppycrawl.tools.checkstyle.api.AutomaticBean

com.puppycrawl.tools.checkstyle.api.AbstractViolationReporter

com.puppycrawl.tools.checkstyle.api.AbstractCheck

com.github.sevntu.checkstyle.checks.coding.NumericLiteralNeedsUnderscoreCheck

All Implemented Interfaces:

com.puppycrawl.tools.checkstyle.api.Configurable, com.puppycrawl.tools.checkstyle.api.Contextualizable

public class NumericLiteralNeedsUnderscoreCheck
extends com.puppycrawl.tools.checkstyle.api.AbstractCheck

This check verifies that large numeric literals are spaced by underscores.

Java 7 allows for underscores to delimit numeric literals to enhance readability because very large numeric literals are hard to read. For example:

long creditCardNumber = 1234_5678_1234_5678L;

is much easier to read than

long creditCardNumber = 1234567812345678L;

This check comes with the following parameters:

"minDecimalSymbolLength" - The minimum number of symbols in a decimal literal (includes int, long, float, and double) before the check begins to look for underscores. Numeric literals with delimiters like decimal points or exponentials will be split before checking the length. Default is 7.

"maxDecimalSymbolsUntilUnderscore" - The maximum number of symbols in a decimal literal allowed before the check demands an underscore. This does not take postfixes and delimiters like decimal points and exponentials into account. Default is 3.

"minHexSymbolLength" - The minimum number of symbols in a hex literal before the check begins to look for underscores. Numeric literals with delimiters like decimal points or exponentials will be split before checking the length. Default is 5.

"maxHexSymbolsUntilUnderscore" - The maximum number of symbols in a hex literal allowed before the check demands an underscore. This does not take the prefix 0x, delimiters like decimal points and exponentials, and postfixes into account. Default is 4.

"minBinarySymbolLength" - The minimum number of symbols in a binary literal before the check begins to look for underscores. Default is 9.

"maxBinarySymbolsUntilUnderscore" - The maximum number of symbols in a binary literal allowed before the check demands an underscore. This does not take the prefix 0b and postfixes into account. Default is 8.

Examples (assuming default parameters):

 // Ignored because length of token is 6, which is less than minDecimalSymbolLength (7)
 int ignoredDecimal = 123456;
 // Ignored because the postfix L is not taken into account
 long ignoredDecimal = 123456L;
 // Ignored because each segment delimited by the decimal point has a length
 // less than minDecimalSymbolLength (7)
 float ignoredDecimal = 123456.123456f;
 // Failed because token does not have underscores every 3 characters
 // (maxDecimalSymbolsUntilUnderscore = 3)
 int failingDecimal = 1234567;
 double failingDecimal = 1.1234567e0d;
 int passingDecimal = 1_234_567;
 double passingDecimal = 123456.123456e0d;
 double passingDecimal = 1.123_456_7e0d;
 int ignoredHex = 0xFFFF;
 int failingHex = 0xFFFFFFFF;
 int passingHex = 0xFFFF_FFFF;
 float passingHex = 0xAAAA.BBBBp1f;
 int ignoredBinary = 0b01010101;
 int failingBinary = 0b0000000000000000;
 int passingBinary = 0b00000000_00000000;
 

An example of how to configure parameters:

 <module name="NumericLiteralNeedsUnderscoreCheck">
    <property name="minDecimalSymbolLength" value="4"/>
    <property name="maxDecimalSymbolsUntilUnderscore" value="3"/>
    <property name="minHexSymbolLength" value="3"/>
    <property name="maxHexSymbolsUntilUnderscore" value="2"/>
    <property name="minBinarySymbolLength" value="5"/>
    <property name="maxBinarySymbolsUntilUnderscore" value="4"/>
 </module>
 

Examples (assuming above parameters):

 // Ignored because length of token is 3, which is less than minDecimalSymbolLength (4)
 int ignoredDecimal = 123;
 // Ignored because each segment delimited by the decimal point has a length
 // less than minDecimalSymbolLength (4)
 float ignoredDecimal = 123.123f;
 // Failed because token does not have underscores every 3 characters
 // (maxDecimalSymbolsUntilUnderscore = 3)
 int failingDecimal = 1234;
 int passingDecimal = 1_234;
 int ignoredHex = 0xFF;
 int failingHex = 0xFFFF;
 int passingHex = 0xFF_FF;
 int ignoredBinary = 0b0101;
 int failingBinary = 0b00001111;
 int passingBinary = 0b0000_1111;
 

Since:

1.18.0

Author:

Cheng-Yu Pai

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected static class	NumericLiteralNeedsUnderscoreCheck.NumericType Type of numeric literal.

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

com.puppycrawl.tools.checkstyle.api.AutomaticBean.OutputStreamOptions

Field Summary

Fields

Modifier and Type	Field and Description
static String	MSG_KEY Key for error message.

Constructor Summary

Constructors

Constructor and Description
NumericLiteralNeedsUnderscoreCheck()

Method Summary

Modifier and Type	Method and Description
int[]	getAcceptableTokens()
int[]	getDefaultTokens()
int[]	getRequiredTokens()
void	setIgnoreFieldNamePattern(String pattern) Sets the regexp pattern for field names to ignore.
void	setMaxBinarySymbolsUntilUnderscore(int amount) Sets how many characters there can be until there must be an underscore (binary literals).
void	setMaxDecimalSymbolsUntilUnderscore(int amount) Sets how many characters there can be until there must be an underscore (for decimal literals).
void	setMaxHexSymbolsUntilUnderscore(int amount) Sets how many characters there can be until there must be an underscore (for hex literals).
void	setMinBinarySymbolLength(int length) Sets how many characters in a byte literal there must be before it checks for an underscore.
void	setMinDecimalSymbolLength(int length) Sets how many characters in a decimal literal there must be before it checks for an underscore.
void	setMinHexSymbolLength(int length) Sets how many characters in a hex literal there must be before it checks for an underscore.
void	visitToken(com.puppycrawl.tools.checkstyle.api.DetailAST ast)

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

beginTree, clearMessages, destroy, finishTree, getFileContents, getLine, getLines, getMessages, getTabWidth, getTokenNames, 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

Methods inherited from class java.lang.Object

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

Field Detail

MSG_KEY

public static final String MSG_KEY

Key for error message.

See Also:

Constant Field Values

Constructor Detail

NumericLiteralNeedsUnderscoreCheck

public NumericLiteralNeedsUnderscoreCheck()

Method Detail

setMinDecimalSymbolLength

public void setMinDecimalSymbolLength(int length)

Sets how many characters in a decimal literal there must be before it checks for an underscore.

Parameters:

length - minimum checking length of the literal

setMaxDecimalSymbolsUntilUnderscore

public void setMaxDecimalSymbolsUntilUnderscore(int amount)

Sets how many characters there can be until there must be an underscore (for decimal literals).

Parameters:

amount - maximum number of characters between underscores

setMinHexSymbolLength

public void setMinHexSymbolLength(int length)

Sets how many characters in a hex literal there must be before it checks for an underscore.

Parameters:

length - minimum checking length of the literal

setMaxHexSymbolsUntilUnderscore

public void setMaxHexSymbolsUntilUnderscore(int amount)

Sets how many characters there can be until there must be an underscore (for hex literals).

Parameters:

amount - maximum number of characters between underscores

setMinBinarySymbolLength

public void setMinBinarySymbolLength(int length)

Sets how many characters in a byte literal there must be before it checks for an underscore.

Parameters:

length - minimum checking length of the literal

setMaxBinarySymbolsUntilUnderscore

public void setMaxBinarySymbolsUntilUnderscore(int amount)

Sets how many characters there can be until there must be an underscore (binary literals).

Parameters:

amount - maximum number of characters between underscores

setIgnoreFieldNamePattern

public void setIgnoreFieldNamePattern(String pattern)

Sets the regexp pattern for field names to ignore.

Parameters:

pattern - the regexp pattern of fields to ignore

getDefaultTokens

public int[] getDefaultTokens()

Specified by:

getDefaultTokens in class com.puppycrawl.tools.checkstyle.api.AbstractCheck

getAcceptableTokens

public int[] getAcceptableTokens()

Specified by:

getAcceptableTokens in class com.puppycrawl.tools.checkstyle.api.AbstractCheck

getRequiredTokens

public int[] getRequiredTokens()

Specified by:

getRequiredTokens in class com.puppycrawl.tools.checkstyle.api.AbstractCheck

visitToken

public void visitToken(com.puppycrawl.tools.checkstyle.api.DetailAST ast)

Overrides:

visitToken in class com.puppycrawl.tools.checkstyle.api.AbstractCheck