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

Class 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. 

     switch (a)
 {
   case 0:
     // Never OK, break outside block
     {
       x = 1;
     }
     break;
   case 1:
     // Never OK, statement outside block
     System.out.println("Hello");
     {
       x = 2;
       break;
     }
   case 2:
     // OK if allowInSwitchCase is true
     {
       System.out.println("Hello");
       x = 3;
       break;
     }
 }
    • 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"/>

    Parent is com.puppycrawl.tools.checkstyle.TreeWalker

    Violation Message Keys:

    • block.nested
    Since:
    3.1

    • Field Detail

      • MSG_KEY_BLOCK_NESTED

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

    • Constructor Detail

      • AvoidNestedBlocksCheck

        public AvoidNestedBlocksCheck()

    • 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

      • 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

      • 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.