Package com.puppycrawl.tools.checkstyle.checks.blocks

Class EmptyCatchBlockCheck

  • All Implemented Interfaces:
    Configurable, Contextualizable
    public class EmptyCatchBlockCheck
extends AbstractCheck

    Checks for empty catch blocks. By default check allows empty catch block with any comment inside.

    There are two options to make validation more precise: exceptionVariableName and commentFormat. If both options are specified - they are applied by any of them is matching.

    • Property exceptionVariableName - Specify the RegExp for the name of the variable associated with exception. If check meets variable name matching specified value - empty block is suppressed. Type is java.util.regex.Pattern. Default value is "^$".
    • Property commentFormat - Specify the RegExp for the first comment inside empty catch block. If check meets comment inside empty catch block matching specified format - empty block is suppressed. If it is multi-line comment - only its first line is analyzed. Type is java.util.regex.Pattern. Default value is ".*".

    To configure the check to suppress empty catch block if exception's variable name is expected or ignore or there's any comment inside: 

     <module name="EmptyCatchBlock">
   <property name="exceptionVariableName" value="expected|ignore"/>
 </module>

    Such empty blocks would be both suppressed: 

     try {
   throw new RuntimeException();
 } catch (RuntimeException expected) {
 }
 try {
   throw new RuntimeException();
 } catch (RuntimeException ignore) {
 }

    To configure the check to suppress empty catch block if single-line comment inside is "//This is expected": 

     <module name="EmptyCatchBlock">
   <property name="commentFormat" value="This is expected"/>
 </module>

    Such empty block would be suppressed: 

     try {
   throw new RuntimeException();
 } catch (RuntimeException ex) {
   //This is expected
 }

    To configure the check to suppress empty catch block if single-line comment inside is "//This is expected" or exception's variable name is "myException" (any option is matching): 

     <module name="EmptyCatchBlock">
   <property name="commentFormat" value="This is expected"/>
   <property name="exceptionVariableName" value="myException"/>
 </module>

    Such empty blocks would be suppressed: 

     try {
   throw new RuntimeException();
 } catch (RuntimeException e) {
   //This is expected
 }
 ...
 try {
   throw new RuntimeException();
 } catch (RuntimeException e) {
   //   This is expected
 }
 ...
 try {
   throw new RuntimeException();
 } catch (RuntimeException e) {
   // This is expected
   // some another comment
 }
 ...
 try {
   throw new RuntimeException();
 } catch (RuntimeException e) {
   /* This is expected */
 }
 ...
 try {
   throw new RuntimeException();
 } catch (RuntimeException e) {
   /*
   *
   * This is expected
   * some another comment
   */
 }
 ...
 try {
   throw new RuntimeException();
 } catch (RuntimeException myException) {

 }

    Parent is com.puppycrawl.tools.checkstyle.TreeWalker

    Violation Message Keys:

    • catch.block.empty
    Since:
    6.4

    • Field Detail

      • MSG_KEY_CATCH_BLOCK_EMPTY

        public static final java.lang.String MSG_KEY_CATCH_BLOCK_EMPTY
        A key is pointing to the warning message text in "messages.properties" file.
        See Also:
        Constant Field Values

    • Constructor Detail

      • EmptyCatchBlockCheck

        public EmptyCatchBlockCheck()

    • Method Detail

      • setExceptionVariableName

        public void setExceptionVariableName​(java.util.regex.Pattern exceptionVariablePattern)
        Setter to specify the RegExp for the name of the variable associated with exception. If check meets variable name matching specified value - empty block is suppressed.
        Parameters:
        exceptionVariablePattern - pattern of exception's variable name.

      • setCommentFormat

        public void setCommentFormat​(java.util.regex.Pattern commentPattern)
        Setter to specify the RegExp for the first comment inside empty catch block. If check meets comment inside empty catch block matching specified format - empty block is suppressed. If it is multi-line comment - only its first line is analyzed.
        Parameters:
        commentPattern - pattern of comment.

      • 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

      • 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

      • 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

      • 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.