Package com.puppycrawl.tools.checkstyle.checks.design

Class ThrowsCountCheck

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.design.ThrowsCountCheck
All Implemented Interfaces:
Configurable, Contextualizable
public final class ThrowsCountCheck extends AbstractCheck
Restricts throws statements to a specified count. Methods with "Override" or "java.lang.Override" annotation are skipped from validation as current class cannot change signature of these methods.

Rationale: Exceptions form part of a method's interface. Declaring a method to throw too many differently rooted exceptions makes exception handling onerous and leads to poor programming practices such as writing code like catch(Exception ex). 4 is the empirical value which is based on reports that we had for the ThrowsCountCheck over big projects such as OpenJDK. This check also forces developers to put exceptions into a hierarchy such that in the simplest case, only one type of exception need be checked for by a caller but any subclasses can be caught specifically if necessary. For more information on rules for the exceptions and their issues, see Effective Java: Programming Language Guide Second Edition by Joshua Bloch pages 264-273.

ignorePrivateMethods - allows to skip private methods as they do not cause problems for other classes.

  • Property ignorePrivateMethods - Allow private methods to be ignored. Type is boolean. Default value is true.
  • Property max - Specify maximum allowed number of throws statements. Type is int. Default value is 4.

Parent is com.puppycrawl.tools.checkstyle.TreeWalker

Violation Message Keys:

  • throws.count
Since:
3.2

  • Field Details

  • Constructor Details

    • ThrowsCountCheck

      public ThrowsCountCheck()
      Creates new instance of the check.

  • 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:

    • setIgnorePrivateMethods

      public void setIgnorePrivateMethods(boolean ignorePrivateMethods)
      Setter to allow private methods to be ignored.
      Parameters:
      ignorePrivateMethods - whether private methods must be ignored.
      Since:
      6.7

    • setMax

      public void setMax(int max)
      Setter to specify maximum allowed number of throws statements.
      Parameters:
      max - maximum allowed throws statements.
      Since:
      3.2

    • 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

    • visitLiteralThrows

      private void visitLiteralThrows(DetailAST ast)
      Checks number of throws statements.
      Parameters:
      ast - throws for check.

    • isOverriding

      private static boolean isOverriding(DetailAST ast)
      Check if a method has annotation @Override.
      Parameters:
      ast - throws, which is being checked.
      Returns:
      true, if a method has annotation @Override.

    • getAnnotationName

      private static String getAnnotationName(DetailAST annotation)
      Gets name of an annotation.
      Parameters:
      annotation - to get name of.
      Returns:
      name of an annotation.

    • isInPrivateMethod

      private static boolean isInPrivateMethod(DetailAST ast)
      Checks if method, which throws an exception is private.
      Parameters:
      ast - throws, which is being checked.
      Returns:
      true, if method, which throws an exception is private.