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

Class FallThroughCheck

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.FallThroughCheck

All Implemented Interfaces:

Configurable, Contextualizable

public class FallThroughCheck
extends AbstractCheck

Checks for fall-through in switch statements. Finds locations where a case contains Java code but lacks a break, return, yield, throw or continue statement.

The check honors special comments to suppress the warning. By default, the texts "fallthru", "fall thru", "fall-thru", "fallthrough", "fall through", "fall-through" "fallsthrough", "falls through", "falls-through" (case-sensitive). The comment containing these words must be all on one line, and must be on the last non-empty line before the case triggering the warning or on the same line before the case(ugly, but possible). Any other comment may follow on the same line.

Note: The check assumes that there is no unreachable code in the case.

• Property checkLastCaseGroup - Control whether the last case group must be checked. Type is boolean. Default value is false.
• Property reliefPattern - Define the RegExp to match the relief comment that suppresses the warning about a fall through. Type is java.util.regex.Pattern. Default value is "falls?[ -]?thr(u|ough)".

Parent is com.puppycrawl.tools.checkstyle.TreeWalker

Violation Message Keys:

• fall.through
• fall.through.last

Since:

3.4

Nested Class Summary

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

AbstractAutomaticBean.OutputStreamOptions

Field Summary

Fields

Modifier and Type	Field	Description
private boolean	checkLastCaseGroup	Control whether the last case group must be checked.
static final String	MSG_FALL_THROUGH	A key is pointing to the warning message text in "messages.properties" file.
static final String	MSG_FALL_THROUGH_LAST	A key is pointing to the warning message text in "messages.properties" file.
private Pattern	reliefPattern	Define the RegExp to match the relief comment that suppresses the warning about a fall through.

Constructor Summary

Constructors

Constructor	Description
FallThroughCheck()

Method Summary

Modifier and Type	Method	Description
private boolean	checkIf(DetailAST ast, boolean useBreak, boolean useContinue, Set<String> labels)	Checks if a given IF terminated by return, throw or, if allowed break, continue.
private boolean	checkLoop(DetailAST ast, Set<String> labels)	Checks if a given loop terminated by return, throw or, if allowed break, continue.
private boolean	checkSlist(DetailAST slistAst, boolean useBreak, boolean useContinue, Set<String> labels)	Checks if a given SLIST terminated by return, throw or, if allowed break, continue.
private boolean	checkSwitch(DetailAST literalSwitchAst, boolean useContinue, Set<String> labels)	Checks if a given switch terminated by return, throw or, if allowed break, continue.
private boolean	checkSynchronized(DetailAST synchronizedAst, boolean useBreak, boolean useContinue, Set<String> labels)	Checks if a given synchronized block terminated by return, throw or, if allowed break, continue.
private boolean	checkTry(DetailAST ast, boolean useBreak, boolean useContinue, Set<String> labels)	Checks if a given try/catch/finally block terminated by return, throw or, if allowed break, continue.
int[]	getAcceptableTokens()	The configurable token set.
int[]	getDefaultTokens()	Returns the default token a check is interested in.
private static DetailAST	getNextNonCommentAst(DetailAST ast)	This method will skip the comment content while finding the next ast of current ast.
int[]	getRequiredTokens()	The tokens that this check must be registered for.
private boolean	hasFallThroughComment(DetailAST currentCase)	Determines if the fall through case between currentCase and nextCase is relieved by an appropriate comment.
private static boolean	hasLabel(DetailAST statement, Set<String> labelsForCurrentSwitchScope)	Checks if given break or continue ast has outer label.
private boolean	hasReliefComment(DetailAST ast)	Check if there is any fall through comment.
boolean	isCommentNodesRequired()	Whether comment nodes are required or not.
private boolean	isTerminated(DetailAST ast, boolean useBreak, boolean useContinue, Set<String> labelsForCurrentSwitchScope)	Checks if a given subtree terminated by return, throw or, if allowed break, continue.
void	setCheckLastCaseGroup(boolean value)	Setter to control whether the last case group must be checked.
void	setReliefPattern(Pattern pattern)	Setter to define the RegExp to match the relief comment that suppresses the warning about a fall through.
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

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_FALL_THROUGH

public static final String MSG_FALL_THROUGH

A key is pointing to the warning message text in "messages.properties" file.

See Also:

• Constant Field Values

MSG_FALL_THROUGH_LAST

public static final String MSG_FALL_THROUGH_LAST

A key is pointing to the warning message text in "messages.properties" file.

See Also:

• Constant Field Values

checkLastCaseGroup

private boolean checkLastCaseGroup

Control whether the last case group must be checked.

reliefPattern

private Pattern reliefPattern

Define the RegExp to match the relief comment that suppresses the warning about a fall through.

Constructor Details

FallThroughCheck

public FallThroughCheck()

Method Details

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

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

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

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.

setReliefPattern

public void setReliefPattern(Pattern pattern)

Setter to define the RegExp to match the relief comment that suppresses the warning about a fall through.

Parameters:

pattern - The regular expression pattern.

Since:

4.0

setCheckLastCaseGroup

public void setCheckLastCaseGroup(boolean value)

Setter to control whether the last case group must be checked.

Parameters:

value - new value of the property.

Since:

4.0

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

isTerminated

private boolean isTerminated(DetailAST ast,
 boolean useBreak,
 boolean useContinue,
 Set<String> labelsForCurrentSwitchScope)

Checks if a given subtree terminated by return, throw or, if allowed break, continue. When analyzing fall-through cases in switch statements, a Set of String labels is used to keep track of the labels encountered in the enclosing switch statements.

Parameters:

ast - root of given subtree

useBreak - should we consider break as terminator

useContinue - should we consider continue as terminator

labelsForCurrentSwitchScope - the Set labels for the current scope of the switch

Returns:

true if the subtree is terminated.

hasLabel

private static boolean hasLabel(DetailAST statement,
 Set<String> labelsForCurrentSwitchScope)

Checks if given break or continue ast has outer label.

Parameters:

statement - break or continue node

labelsForCurrentSwitchScope - the Set labels for the current scope of the switch

Returns:

true if local label used

checkSlist

private boolean checkSlist(DetailAST slistAst,
 boolean useBreak,
 boolean useContinue,
 Set<String> labels)

Checks if a given SLIST terminated by return, throw or, if allowed break, continue.

Parameters:

slistAst - SLIST to check

useBreak - should we consider break as terminator

useContinue - should we consider continue as terminator

labels - label names

Returns:

true if SLIST is terminated.

checkIf

private boolean checkIf(DetailAST ast,
 boolean useBreak,
 boolean useContinue,
 Set<String> labels)

Checks if a given IF terminated by return, throw or, if allowed break, continue.

Parameters:

ast - IF to check

useBreak - should we consider break as terminator

useContinue - should we consider continue as terminator

labels - label names

Returns:

true if IF is terminated.

getNextNonCommentAst

private static DetailAST getNextNonCommentAst(DetailAST ast)

This method will skip the comment content while finding the next ast of current ast.

Parameters:

ast - current ast

Returns:

next ast after skipping comment

checkLoop

private boolean checkLoop(DetailAST ast,
 Set<String> labels)

Checks if a given loop terminated by return, throw or, if allowed break, continue.

Parameters:

ast - loop to check

labels - label names

Returns:

true if loop is terminated.

checkTry

private boolean checkTry(DetailAST ast,
 boolean useBreak,
 boolean useContinue,
 Set<String> labels)

Checks if a given try/catch/finally block terminated by return, throw or, if allowed break, continue.

Parameters:

ast - loop to check

useBreak - should we consider break as terminator

useContinue - should we consider continue as terminator

labels - label names

Returns:

true if try/catch/finally block is terminated

checkSwitch

private boolean checkSwitch(DetailAST literalSwitchAst,
 boolean useContinue,
 Set<String> labels)

Checks if a given switch terminated by return, throw or, if allowed break, continue.

Parameters:

literalSwitchAst - loop to check

useContinue - should we consider continue as terminator

labels - label names

Returns:

true if switch is terminated

checkSynchronized

private boolean checkSynchronized(DetailAST synchronizedAst,
 boolean useBreak,
 boolean useContinue,
 Set<String> labels)

Checks if a given synchronized block terminated by return, throw or, if allowed break, continue.

Parameters:

synchronizedAst - synchronized block to check.

useBreak - should we consider break as terminator

useContinue - should we consider continue as terminator

labels - label names

Returns:

true if synchronized block is terminated

hasFallThroughComment

private boolean hasFallThroughComment(DetailAST currentCase)

Determines if the fall through case between currentCase and nextCase is relieved by an appropriate comment.

Handles

 case 1:
 /* FALLTHRU */ case 2:

 switch(i) {
 default:
 /* FALLTHRU */}

 case 1:
 // FALLTHRU
 case 2:

 switch(i) {
 default:
 // FALLTHRU
 

Parameters:

currentCase - AST of the case that falls through to the next case.

Returns:

True if a relief comment was found

hasReliefComment

private boolean hasReliefComment(DetailAST ast)

Check if there is any fall through comment.

Parameters:

ast - ast to check

Returns:

true if relief comment found