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 Details

    • MSG_KEY_CATCH_BLOCK_EMPTY

      public static final String MSG_KEY_CATCH_BLOCK_EMPTY
      A key is pointing to the warning message text in "messages.properties" file.
      See Also:
  • Constructor Details

    • EmptyCatchBlockCheck

      public EmptyCatchBlockCheck()
  • Method Details

    • setExceptionVariableName

      public void setExceptionVariableName(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(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:
    • 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:
    • 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:
    • 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.
    • 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