Class ThrowsCountCheck

  • All Implemented Interfaces:
    Configurable, Contextualizable

    public final class ThrowsCountCheck
    extends AbstractCheck

    Restricts throws statements to a specified count (default = 4). 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 methods interface. Declaring a method to throw too many differently rooted exceptions makes exception handling onerous and leads to poor programming practices such as catch (Exception). 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 allows any sub-classes to 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.

    • 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
      • DEFAULT_MAX

        private static final int DEFAULT_MAX
        Default value of max property.
        See Also:
        Constant Field Values
      • ignorePrivateMethods

        private boolean ignorePrivateMethods
        Whether private methods must be ignored.
      • max

        private int max
        Maximum allowed throws statements.
    • Constructor Detail

      • ThrowsCountCheck

        public ThrowsCountCheck()
        Creates new instance of the check.
    • 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
      • setIgnorePrivateMethods

        public void setIgnorePrivateMethods​(boolean ignorePrivateMethods)
        Sets whether private methods must be ignored.
        Parameters:
        ignorePrivateMethods - whether private methods must be ignored.
      • setMax

        public void setMax​(int max)
        Setter for max property.
        Parameters:
        max - maximum allowed throws statements.
      • 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 java.lang.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.