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

Class AvoidNestedBlocksCheck

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.blocks.AvoidNestedBlocksCheck
All Implemented Interfaces:
Configurable, Contextualizable
public class AvoidNestedBlocksCheck extends AbstractCheck

Finds nested blocks (blocks that are used freely in the code).

Rationale: Nested blocks are often leftovers from the debugging process, they confuse the reader.

For example, this check finds the obsolete braces in 

 public void guessTheOutput()
 {
   int whichIsWhich = 0;
   {
     whichIsWhich = 2;
   }
   System.out.println("value = " + whichIsWhich);
 }

and debugging / refactoring leftovers such as 

 // if (conditionThatIsNotUsedAnyLonger)
 {
   System.out.println("unconditional");
 }

A case in a switch statement does not implicitly form a block. Thus to be able to introduce local variables that have case scope it is necessary to open a nested block. This is supported, set the allowInSwitchCase property to true and include all statements of the case in the block.

  • Property allowInSwitchCase - Allow nested blocks if they are the only child of a switch case. Type is boolean. Default value is false.

To configure the check: 

 <module name="AvoidNestedBlocks"/>

Example: 

 public void foo() {
   int myInteger = 0;
   {                      // violation
     myInteger = 2;
   }
   System.out.println("myInteger = " + myInteger);

   switch (a) {
     case 1:
       {                    // violation
         System.out.println("Case 1");
         break;
       }
     case 2:
       System.out.println("Case 2");     // OK
       break;
   }
 }

To configure the check to allow nested blocks in switch case: 

 <module name="AvoidNestedBlocks">
   <property name="allowInSwitchCase" value="true"/>
 </module>

Example: 

 public void foo() {
   int myInteger = 0;
   {                      // violation
     myInteger = 2;
   }
   System.out.println("myInteger = " + myInteger);

   switch (a)
   {
     case 1:
       {                    // OK
         System.out.println("Case 1");
         break;
       }
     case 2:
       System.out.println("Case 2");     // OK
       break;
   }
 }

Parent is com.puppycrawl.tools.checkstyle.TreeWalker

Violation Message Keys:

  • block.nested
Since:
3.1

  • Field Details

    • MSG_KEY_BLOCK_NESTED

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

    • allowInSwitchCase

      private boolean allowInSwitchCase
      Allow nested blocks if they are the only child of a switch case.

  • Constructor Details

    • AvoidNestedBlocksCheck

      public AvoidNestedBlocksCheck()

  • 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:

    • 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:

    • 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

    • hasSiblings

      private static boolean hasSiblings(DetailAST ast)
      Checks whether the AST node has any siblings or not.
      Parameters:
      ast - node to examine
      Returns:
      true if the node has one or more siblings

    • setAllowInSwitchCase

      public void setAllowInSwitchCase(boolean allowInSwitchCase)
      Setter to allow nested blocks if they are the only child of a switch case.
      Parameters:
      allowInSwitchCase - whether nested blocks are allowed if they are the only child of a switch case.