Class TrailingCommentCheck
- java.lang.Object
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- com.puppycrawl.tools.checkstyle.AbstractAutomaticBean
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- com.puppycrawl.tools.checkstyle.api.AbstractViolationReporter
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- com.puppycrawl.tools.checkstyle.api.AbstractCheck
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- com.puppycrawl.tools.checkstyle.checks.TrailingCommentCheck
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- All Implemented Interfaces:
Configurable
,Contextualizable
public class TrailingCommentCheck extends AbstractCheck
The check to ensure that lines with code do not end with comment. For the case of//
comments that means that the only thing that should precede it is whitespace. It doesn't check comments if they do not end a line; for example, it accepts the following:Thread.sleep( 10 /*some comment here*/ );
Format property is intended to deal with the} // while
example.Rationale: Steve McConnell in Code Complete suggests that endline comments are a bad practice. An end line comment would be one that is on the same line as actual code. For example:
a = b + c; // Some insightful comment d = e / f; // Another comment for this line
Quoting Code Complete for the justification:
- "The comments have to be aligned so that they do not interfere with the visual structure of the code. If you don't align them neatly, they'll make your listing look like it's been through a washing machine."
- "Endline comments tend to be hard to format...It takes time to align them. Such time is not spent learning more about the code; it's dedicated solely to the tedious task of pressing the spacebar or tab key."
- "Endline comments are also hard to maintain. If the code on any line containing an endline comment grows, it bumps the comment farther out, and all the other endline comments will have to bumped out to match. Styles that are hard to maintain aren't maintained...."
- "Endline comments also tend to be cryptic. The right side of the line doesn't offer much room and the desire to keep the comment on one line means the comment must be short. Work then goes into making the line as short as possible instead of as clear as possible. The comment usually ends up as cryptic as possible...."
- "A systemic problem with endline comments is that it's hard to write a meaningful comment for one line of code. Most endline comments just repeat the line of code, which hurts more than it helps."
McConnell's comments on being hard to maintain when the size of the line changes are even more important in the age of automated refactorings.
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Property
format
- Specify pattern for strings allowed before the comment. Type isjava.util.regex.Pattern
. Default value is"^[\s});]*$"
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Property
legalComment
- Define pattern for text allowed in trailing comments. This pattern will not be applied to multiline comments. Type isjava.util.regex.Pattern
. Default value isnull
.
Parent is
com.puppycrawl.tools.checkstyle.TreeWalker
Violation Message Keys:
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trailing.comments
- Since:
- 3.4
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Nested Class Summary
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Nested classes/interfaces inherited from class com.puppycrawl.tools.checkstyle.AbstractAutomaticBean
AbstractAutomaticBean.OutputStreamOptions
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Field Summary
Fields Modifier and Type Field Description private Pattern
format
Specify pattern for strings allowed before the comment.private static Pattern
FORMAT_LINE
Specify pattern for strings to be formatted without comment specifiers.private Pattern
legalComment
Define pattern for text allowed in trailing comments.static String
MSG_KEY
A key is pointing to the warning message text in "messages.properties" file.
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Constructor Summary
Constructors Constructor Description TrailingCommentCheck()
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description private void
checkBlockComment(DetailAST ast)
Method to check if block comment is in correct format.private void
checkSingleLineComment(DetailAST ast)
Checks if single-line comment is legal.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.boolean
isCommentNodesRequired()
Whether comment nodes are required or not.private boolean
isLegalCommentContent(String commentContent)
Checks if given comment content is legal.void
setFormat(Pattern pattern)
Setter to specify pattern for strings allowed before the comment.void
setLegalComment(Pattern legalComment)
Setter to define pattern for text allowed in trailing comments.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, init, leaveToken, log, log, log, setFileContents, setTabWidth, setTokens
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Methods inherited from class com.puppycrawl.tools.checkstyle.api.AbstractViolationReporter
finishLocalSetup, getCustomMessages, getId, getMessageBundle, getSeverity, getSeverityLevel, setId, setSeverity
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Methods inherited from class com.puppycrawl.tools.checkstyle.AbstractAutomaticBean
configure, contextualize, getConfiguration, setupChild
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Field Detail
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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
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FORMAT_LINE
private static final Pattern FORMAT_LINE
Specify pattern for strings to be formatted without comment specifiers.
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legalComment
private Pattern legalComment
Define pattern for text allowed in trailing comments. This pattern will not be applied to multiline comments.
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Constructor Detail
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TrailingCommentCheck
public TrailingCommentCheck()
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Method Detail
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setLegalComment
public void setLegalComment(Pattern legalComment)
Setter to define pattern for text allowed in trailing comments. This pattern will not be applied to multiline comments.- Parameters:
legalComment
- pattern to set.- Since:
- 4.2
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setFormat
public final void setFormat(Pattern pattern)
Setter to specify pattern for strings allowed before the comment.- Parameters:
pattern
- a pattern- Since:
- 3.4
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isCommentNodesRequired
public boolean isCommentNodesRequired()
Description copied from class:AbstractCheck
Whether comment nodes are required or not.- Overrides:
isCommentNodesRequired
in classAbstractCheck
- Returns:
- false as a default value.
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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:
TokenTypes
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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:
TokenTypes
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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:
TokenTypes
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visitToken
public void visitToken(DetailAST ast)
Description copied from class:AbstractCheck
Called to process a token.- Overrides:
visitToken
in classAbstractCheck
- Parameters:
ast
- the token to process
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checkSingleLineComment
private void checkSingleLineComment(DetailAST ast)
Checks if single-line comment is legal.- Parameters:
ast
- Detail ast element to be checked.
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checkBlockComment
private void checkBlockComment(DetailAST ast)
Method to check if block comment is in correct format.- Parameters:
ast
- Detail ast element to be checked.
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isLegalCommentContent
private boolean isLegalCommentContent(String commentContent)
Checks if given comment content is legal.- Parameters:
commentContent
- comment content to check.- Returns:
- true if the content is legal.
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