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

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 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 Detail

      • MSG_KEY

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

    • Constructor Detail

      • NoWhitespaceBeforeCheck

        public NoWhitespaceBeforeCheck()

    • 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

      • 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.