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

Class FallThroughCheck

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.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, 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). 

 switch (i) {
 case 0:
   i++; // fall through

 case 1:
   i++;
   // falls through
 case 2:
 case 3:
 case 4: {
   i++;
 }
 // fallthrough
 case 5:
   i++;
 /* fallthru */case 6:
   i++;
 // fall-through
 case 7:
   i++;
   break;
 }

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

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

 case 3:
     x = 2;
     // fallthru
 case 4:
 case 5: // violation
 case 6:
     break;
  • 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)".

To configure the check: 

 <module name="FallThrough"/>

or 

 <module name="FallThrough">
   <property name="reliefPattern" value="continue in next case"/>
 </module>

Parent is com.puppycrawl.tools.checkstyle.TreeWalker

Violation Message Keys:

  • fall.through
  • fall.through.last
Since:
3.4

  • 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:

    • 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:

  • 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:

    • 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:

    • 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:

    • 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.

    • setCheckLastCaseGroup

      public void setCheckLastCaseGroup(boolean value)
      Setter to control whether the last case group must be checked.
      Parameters:
      value - new value of the property.

    • 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