TrailingCommentCheck (checkstyle 9.3 API)

java.lang.Object
- com.puppycrawl.tools.checkstyle.api.AutomaticBean
- - com.puppycrawl.tools.checkstyle.api.AbstractViolationReporter
  - - com.puppycrawl.tools.checkstyle.api.AbstractCheck
    - - com.puppycrawl.tools.checkstyle.checks.TrailingCommentCheck

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.
- Property format - Specify pattern for strings allowed before the comment. Type is java.util.regex.Pattern. Default value is "^[\s});]*$".
- Property legalComment - Define pattern for text allowed in trailing comments. This pattern will not be applied to multiline comments. Type is java.util.regex.Pattern. Default value is null.
To configure the check:
```
 <module name="TrailingComment"/>
 
```
To configure the check so it enforces only comment on a line:
```
 <module name="TrailingComment">
   <property name="format" value="^\\s*$"/>
 </module>
 
```
Example for trailing comments check to suppress specific trailing comment:
```
 public class Test {
   int a; // SUPPRESS CHECKSTYLE
   int b; // NOPMD
   int c; // NOSONAR
   int d; // violation, not suppressed
 }
 
```
To configure check so that trailing comment with exact comments like "SUPPRESS CHECKSTYLE", "NOPMD", "NOSONAR" are suppressed:
```
 <module name="TrailingComment"/>
 <module name="SuppressionXpathSingleFilter">
   <property name="checks" value="TrailingCommentCheck"/>
   <property name="query" value="//SINGLE_LINE_COMMENT
       [./COMMENT_CONTENT[@text=' NOSONAR\n' or @text=' NOPMD\n'
       or @text=' SUPPRESS CHECKSTYLE\n']]"/>
 </module>
 
```
To configure check so that trailing comment starting with "SUPPRESS CHECKSTYLE", "NOPMD", "NOSONAR" are suppressed:
```
 <module name="TrailingComment"/> <module name="SuppressionXpathSingleFilter">
 <property name="checks" value="TrailingCommentCheck"/>
   <property name="query" value="//SINGLE_LINE_COMMENT
       [./COMMENT_CONTENT[starts-with(@text, ' NOPMD')]]"/>
   <property name="query" value="//SINGLE_LINE_COMMENT
       [./COMMENT_CONTENT[starts-with(@text, ' SUPPRESS CHECKSTYLE')]]"/>
   <property name="query" value="//SINGLE_LINE_COMMENT
       [./COMMENT_CONTENT[starts-with(@text, ' NOSONAR')]]"/>
 </module>
 
```
Parent is com.puppycrawl.tools.checkstyle.TreeWalker

Violation Message Keys:
- trailing.comments
Since:

3.4

Nested Class Summary
- Nested classes/interfaces inherited from class com.puppycrawl.tools.checkstyle.api.AutomaticBean
  AutomaticBean.OutputStreamOptions

Field Summary

Fields
Modifier and Type	Field and Description
`private java.util.regex.Pattern`	`format` Specify pattern for strings allowed before the comment.
`private static java.util.regex.Pattern`	`FORMAT_LINE` Specify pattern for strings to be formatted without comment specifiers.
`private java.util.regex.Pattern`	`legalComment` Define pattern for text allowed in trailing comments.
`static java.lang.String`	`MSG_KEY` A key is pointing to the warning message text in "messages.properties" file.

Constructor Summary

Constructors
Constructor and Description

TrailingCommentCheck()

Constructors
Constructor and Description
`TrailingCommentCheck()`

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and 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(java.lang.String commentContent)` Checks if given comment content is legal.
`void`	`setFormat(java.util.regex.Pattern pattern)` Setter to specify pattern for strings allowed before the comment.
`void`	`setLegalComment(java.util.regex.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, getLine, getLineCodePoints, getLines, getTabWidth, getTokenNames, getViolations, init, 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 java.lang.String MSG_KEY
```
    A key is pointing to the warning message text in "messages.properties" file.
    
    See Also:
    
    Constant Field Values
  - FORMAT_LINE
```
private static final java.util.regex.Pattern FORMAT_LINE
```
    Specify pattern for strings to be formatted without comment specifiers.
  - legalComment
```
private java.util.regex.Pattern legalComment
```
    Define pattern for text allowed in trailing comments. This pattern will not be applied to multiline comments.
  - format
```
private java.util.regex.Pattern format
```
    Specify pattern for strings allowed before the comment.
- Constructor Detail
  - TrailingCommentCheck
```
public TrailingCommentCheck()
```
- Method Detail
  - setLegalComment
```
public void setLegalComment(java.util.regex.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.
  - setFormat
```
public final void setFormat(java.util.regex.Pattern pattern)
```
    Setter to specify pattern for strings allowed before the comment.
    
    Parameters:
    
    pattern - a pattern
  - 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.
  - 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
  - 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
  - checkSingleLineComment
```
private void checkSingleLineComment(DetailAST ast)
```
    Checks if single line comment is legal.
    
    Parameters:
    
    ast - Detail ast element to be checked.
  - checkBlockComment
```
private void checkBlockComment(DetailAST ast)
```
    Method to check if block comment is in correct format.
    
    Parameters:
    
    ast - Detail ast element to be checked.
  - isLegalCommentContent
```
private boolean isLegalCommentContent(java.lang.String commentContent)
```
    Checks if given comment content is legal.
    
    Parameters:
    
    commentContent - comment content to check.
    
    Returns:
    
    true if the content is legal.

Class TrailingCommentCheck

Nested Class Summary

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

Field Summary

Constructor Summary

Method Summary

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

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

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

Methods inherited from class java.lang.Object

Field Detail

MSG_KEY

FORMAT_LINE

legalComment

format

Constructor Detail

TrailingCommentCheck

Method Detail

setLegalComment

setFormat

isCommentNodesRequired

getDefaultTokens

getAcceptableTokens

getRequiredTokens

visitToken

checkSingleLineComment

checkBlockComment

isLegalCommentContent