NoWhitespaceBefore

Since Checkstyle 3.0

Description

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.

Properties

name description type default value since
allowLineBreaks Control whether whitespace is allowed if the token is at a linebreak. boolean false 3.0
tokens tokens to check subset of tokens COMMA , SEMI , POST_INC , POST_DEC , DOT , GENERIC_START , GENERIC_END , ELLIPSIS , LABELED_STAT , METHOD_REF . COMMA , SEMI , POST_INC , POST_DEC , ELLIPSIS , LABELED_STAT . 3.0

Examples

To configure the check: 

<module name="Checker">
  <module name="TreeWalker">
    <module name="NoWhitespaceBefore"/>
  </module>
</module>

Example:

class Example1 {
  int foo = 5;
  void example() {
    foo ++; // violation 'is preceded with whitespace'
    foo++;
    for (int i = 0 ; i < 5; i++) {}  // violation '';' is preceded with whitespace'
    for (int i = 0; i < 5; i++) {}
    int[][] array = { { 1, 2 }
                    , { 3, 4 } }; // violation '',' is preceded with whitespace'
    int[][] array2 = { { 1, 2 },
                       { 3, 4 } };
    Lists.charactersOf("foo").listIterator()
           .forEachRemaining(System.out::print)
           ; // violation '';' is preceded with whitespace'
    {
      label1 : // violation '':' is preceded with whitespace'
      for (int i = 0; i < 10; i++) {}
    }

    {
      label2:
      while (foo < 5) {}
    }
  }
}

To configure the check to allow linebreaks before default tokens: 

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

Example:

class Example2 {
  int[][] array = { { 1, 2 }
                  , { 3, 4 } };
  int[][] array2 = { { 1, 2 },
                     { 3, 4 } };
  void ellipsisExample(String ...params) {};
  // violation above ''...' is preceded with whitespace'
  void ellipsisExample2(String
                          ...params) {
    Lists.charactersOf("foo")
         .listIterator()
         .forEachRemaining(System.out::print);
  };
}

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

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

Example:

class Example3 {
  void example() {
    Lists.charactersOf("foo").listIterator()
         .forEachRemaining(System.out::print);
    // violation above ''.' is preceded with whitespace'
    Lists.charactersOf("foo").listIterator().forEachRemaining(System.out ::print);
    // violation above ''::' is preceded with whitespace'
    Lists.charactersOf("foo").listIterator().forEachRemaining(System.out::print);
  }
}

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

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

Example:

class Example4 {
  void example() {
    Lists .charactersOf("foo") // violation ''.' is preceded with whitespace'
          .listIterator()
          .forEachRemaining(System.out ::print);
    // violation above ''::' is preceded with whitespace'
    Lists.charactersOf("foo")
         .listIterator()
         .forEachRemaining(System.out::print);
  }
}

Example of Usage

Violation Messages

All messages can be customized if the default message doesn't suit you. Please see the documentation to learn how to.

Package

com.puppycrawl.tools.checkstyle.checks.whitespace

Parent Module

TreeWalker