Class 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 semicolons 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 Detail

      • allowLineBreaks

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

      • 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
      • 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.