Class ArrayTrailingCommaCheck
- All Implemented Interfaces:
Configurable
,Contextualizable
Checks that array initialization contains a trailing comma.
int[] a = new int[] { 1, 2, 3, };
By default, the check demands a comma at the end if neither left nor right curly braces are on the same line as the last element of the array.
return new int[] { 0 }; return new int[] { 0 }; return new int[] { 0 };
Rationale: Putting this comma in makes it easier to change the order of the elements or add new elements on the end. Main benefit of a trailing comma is that when you add new entry to an array, no surrounding lines are changed.
{ 100000000000000000000, 200000000000000000000, // OK } { 100000000000000000000, 200000000000000000000, 300000000000000000000, // Just this line added, no other changes }
If closing brace is on the same line as trailing comma, this benefit is gone (as the check does not demand a certain location of curly braces the following two cases will not produce a violation):
{100000000000000000000, 200000000000000000000,} // Trailing comma not needed, line needs to be modified anyway {100000000000000000000, 200000000000000000000, // Modified line 300000000000000000000,} // Added line
If opening brace is on the same line as trailing comma there's also (more arguable) problem:
{100000000000000000000, // Line cannot be just duplicated to slightly modify entry } {100000000000000000000, 100000000000000000001, // More work needed to duplicate }
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Property
alwaysDemandTrailingComma
- Control whether to always check for a trailing comma, even when an array is inline. Type isboolean
. Default value isfalse
.
To configure the check:
<module name="ArrayTrailingComma"/>
Which results in the following violations:
int[] numbers = {1, 2, 3}; //no violation boolean[] bools = { true, true, false }; //violation String[][] text = {{},{},}; //no violation double[][] decimals = { {0.5, 2.3, 1.1,}, //no violation {1.7, 1.9, 0.6}, {0.8, 7.4, 6.5} }; // violation as previous line misses a comma char[] chars = {'a', 'b', 'c' }; / /no violation String[] letters = { "a", "b", "c"}; // no violation int[] a1 = new int[]{ 1, 2 , }; // no violation int[] a2 = new int[]{ 1, 2 ,}; // no violation
To configure check to always validate trailing comma:
<module name="ArrayTrailingComma"> <property name="alwaysDemandTrailingComma" value="true"/> </module>
Example:
int[] numbers = {1, 2, 3}; // violation boolean[] bools = { true, true, false // violation }; String[][] text = {{},{},}; // OK double[][] decimals = { {0.5, 2.3, 1.1,}, // OK {1.7, 1.9, 0.6}, // violation {0.8, 7.4, 6.5} // violation }; // violation, previous line misses a comma char[] chars = {'a', 'b', 'c' // violation }; String[] letters = { "a", "b", "c"}; // violation int[] a1 = new int[]{ 1, 2 , }; // OK int[] a2 = new int[]{ 1, 2 ,}; // OK
Parent is com.puppycrawl.tools.checkstyle.TreeWalker
Violation Message Keys:
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array.trailing.comma
- Since:
- 3.2
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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
Fields -
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionint[]
The configurable token set.int[]
Returns the default token a check is interested in.int[]
The tokens that this check must be registered for.void
setAlwaysDemandTrailingComma
(boolean alwaysDemandTrailingComma) Setter to control whether to always check for a trailing comma, even when an array is inline.void
visitToken
(DetailAST arrayInit) Called to process a token.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
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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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Constructor Details
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ArrayTrailingCommaCheck
public ArrayTrailingCommaCheck()
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Method Details
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setAlwaysDemandTrailingComma
public void setAlwaysDemandTrailingComma(boolean alwaysDemandTrailingComma) Setter to control whether to always check for a trailing comma, even when an array is inline.- Parameters:
alwaysDemandTrailingComma
- whether to always check for a trailing comma.
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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:
arrayInit
- the token to process
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