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

Class 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, throw or continue statement.

    The check honors special comments to suppress warnings about the fall through. By default the comments "fallthru", "fall through", "falls through" and "fallthrough" are recognized.

    The following fragment of code will NOT trigger the check, because of the comment "fallthru" and absence of any Java code in case 5. 

     case 3:
     x = 2;
     // fallthru
 case 4:
 case 5:
 case 6:
     break;

    The recognized relief comment can be configured with the property reliefPattern. Default value of this regular expression is "fallthru|fall through|fallthrough|falls through".

    An example of how to configure the check is: 

     <module name="FallThrough">
     <property name="reliefPattern"
                  value="Fall Through"/>
 </module>

    • Field Detail

      • MSG_FALL_THROUGH

        public static final java.lang.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 java.lang.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
        Do we need to check last case group.

      • reliefPattern

        private java.util.regex.Pattern reliefPattern
        Relief regexp to allow fall through to the next case branch.

    • Constructor Detail

      • FallThroughCheck

        public FallThroughCheck()

    • Method Detail

      • 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

      • setReliefPattern

        public void setReliefPattern​(java.util.regex.Pattern pattern)
        Set the relief pattern.
        Parameters:
        pattern - The regular expression pattern.

      • setCheckLastCaseGroup

        public void setCheckLastCaseGroup​(boolean value)
        Configures whether we need to check last case group or not.
        Parameters:
        value - new value of the property.

      • isTerminated

        private boolean isTerminated​(DetailAST ast,
                             boolean useBreak,
                             boolean useContinue)
        Checks if a given subtree terminated by return, throw or, if allowed break, continue.
        Parameters:
        ast - root of given subtree
        useBreak - should we consider break as terminator.
        useContinue - should we consider continue as terminator.
        Returns:
        true if the subtree is terminated.

      • checkSlist

        private boolean checkSlist​(DetailAST slistAst,
                           boolean useBreak,
                           boolean useContinue)
        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.
        Returns:
        true if SLIST is terminated.

      • checkIf

        private boolean checkIf​(DetailAST ast,
                        boolean useBreak,
                        boolean useContinue)
        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.
        Returns:
        true if IF is terminated.

      • checkLoop

        private boolean checkLoop​(DetailAST ast)
        Checks if a given loop terminated by return, throw or, if allowed break, continue.
        Parameters:
        ast - loop to check
        Returns:
        true if loop is terminated.

      • checkTry

        private boolean checkTry​(DetailAST ast,
                         boolean useBreak,
                         boolean useContinue)
        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.
        Returns:
        true if try/catch/finally block is terminated.

      • checkSwitch

        private boolean checkSwitch​(DetailAST literalSwitchAst,
                            boolean useContinue)
        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.
        Returns:
        true if switch is terminated.

      • hasFallThroughComment

        private boolean hasFallThroughComment​(DetailAST currentCase,
                                      DetailAST nextCase)
        Determines if the fall through case between currentCase and nextCase is relieved by a appropriate comment.
        Parameters:
        currentCase - AST of the case that falls through to the next case.
        nextCase - AST of the next case.
        Returns:
        True if a relief comment was found

      • matchesComment

        private boolean matchesComment​(java.util.regex.Pattern pattern,
                               java.lang.String line,
                               int lineNo)
        Does a regular expression match on the given line and checks that a possible match is within a comment.
        Parameters:
        pattern - The regular expression pattern to use.
        line - The line of test to do the match on.
        lineNo - The line number in the file.
        Returns:
        True if a match was found inside a comment.