Package com.puppycrawl.tools.checkstyle.checks.whitespace

Class NoWhitespaceBeforeCheck

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.whitespace.NoWhitespaceBeforeCheck
All Implemented Interfaces:
Configurable, Contextualizable
public class NoWhitespaceBeforeCheck extends AbstractCheck

Checks that there is no whitespace before a token. More specifically, it checks that it is not preceded with whitespace, or (if linebreaks are allowed) all characters on the line before are whitespace. To allow linebreaks before a token, set property allowLineBreaks to true. No check occurs before semi-colons in empty for loop initializers or conditions.

  • Property allowLineBreaks - Control whether whitespace is allowed if the token is at a linebreak. Type is boolean. Default value is false.
  • Property tokens - tokens to check Type is java.lang.String[]. Validation type is tokenSet. Default value is: COMMA, SEMI, POST_INC, POST_DEC, ELLIPSIS, LABELED_STAT.

To configure the check: 

 <module name="NoWhitespaceBefore"/>

Example:

 int foo;
 foo ++; // violation, whitespace before '++' is not allowed
 foo++; // OK
 for (int i = 0 ; i < 5; i++) {}  // violation
            // ^ whitespace before ';' is not allowed
 for (int i = 0; i < 5; i++) {} // OK
 int[][] array = { { 1, 2 }
                 , { 3, 4 } }; // violation, whitespace before ',' is not allowed
 int[][] array2 = { { 1, 2 },
                    { 3, 4 } }; // OK
 Lists.charactersOf("foo").listIterator()
        .forEachRemaining(System.out::print)
        ; // violation, whitespace before ';' is not allowed
   {
     label1 : // violation, whitespace before ':' is not allowed
     for (int i = 0; i < 10; i++) {}
   }

   {
     label2: // OK
     while (true) {}
   }

To configure the check to allow linebreaks before default tokens:

 <module name="NoWhitespaceBefore">
   <property name="allowLineBreaks" value="true"/>
 </module>

Example:

 int[][] array = { { 1, 2 }
                 , { 3, 4 } }; // OK, linebreak is allowed before ','
 int[][] array2 = { { 1, 2 },
                    { 3, 4 } }; // OK, ideal code
 void ellipsisExample(String ...params) {}; // violation, whitespace before '...' is not allowed
 void ellipsisExample2(String
                         ...params) {}; //OK, linebreak is allowed before '...'
 Lists.charactersOf("foo")
        .listIterator()
        .forEachRemaining(System.out::print); // OK

To Configure the check to restrict the use of whitespace before METHOD_REF and DOT tokens: 

 <module name="NoWhitespaceBefore">
   <property name="tokens" value="METHOD_REF"/>
   <property name="tokens" value="DOT"/>
 </module>

Example:

 Lists.charactersOf("foo").listIterator()
        .forEachRemaining(System.out::print); // violation, whitespace before '.' is not allowed
 Lists.charactersOf("foo").listIterator().forEachRemaining(System.out ::print); // violation,
                           // whitespace before '::' is not allowed  ^
 Lists.charactersOf("foo").listIterator().forEachRemaining(System.out::print); // OK

To configure the check to allow linebreak before METHOD_REF and DOT tokens: 

 <module name="NoWhitespaceBefore">
   <property name="tokens" value="METHOD_REF"/>
   <property name="tokens" value="DOT"/>
   <property name="allowLineBreaks" value="true"/>
 </module>

Example:

 Lists .charactersOf("foo") //violation, whitespace before '.' is not allowed
         .listIterator()
         .forEachRemaining(System.out ::print); // violation,
                                  // ^ whitespace before '::' is not allowed
 Lists.charactersOf("foo")
        .listIterator()
        .forEachRemaining(System.out::print); // OK

Parent is com.puppycrawl.tools.checkstyle.TreeWalker

Violation Message Keys:

  • ws.preceded
Since:
3.0

  • Field Details

    • MSG_KEY

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

    • allowLineBreaks

      private boolean allowLineBreaks
      Control whether whitespace is allowed if the token is at a linebreak.

  • Constructor Details

    • NoWhitespaceBeforeCheck

      public NoWhitespaceBeforeCheck()

  • 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

    • isInEmptyForInitializerOrCondition

      private static boolean isInEmptyForInitializerOrCondition(DetailAST semicolonAst)
      Checks that semicolon is in empty for initializer or condition.
      Parameters:
      semicolonAst - DetailAST of semicolon.
      Returns:
      true if semicolon is in empty for initializer or condition.

    • setAllowLineBreaks

      public void setAllowLineBreaks(boolean allowLineBreaks)
      Setter to control whether whitespace is allowed if the token is at a linebreak.
      Parameters:
      allowLineBreaks - whether whitespace should be flagged at line breaks.