Description

Checks whether files end with a new line.

Rationale: Any source files and text files in general should end with a newline character, especially when using SCM systems such as CVS. CVS will even print a warning when it encounters a file that doesn't end with a newline.

Properties

Examples

To configure the check:

<module name="NewlineAtEndOfFile"/>
        

To configure the check to always use Unix-style line separators:

<module name="NewlineAtEndOfFile">
    <property name="lineSeparator" value="lf"/>
</module>
        

To configure the check to work only on java, xml and python files:

<module name="NewlineAtEndOfFile">
    <property name="fileExtensions" value="java, xml, py"/>
</module>
          

Package

com.puppycrawl.tools.checkstyle.checks

Parent Module

Checker

Description

A check for TODO: comments. Actually it is a generic regular expression matcher on Java comments. To check for other patterns in Java comments, set property format.

Properties

Notes

Using TODO: comments is a great way to keep track of tasks that need to be done. Having them reported by Checkstyle makes it very hard to forget about them.

Examples

To configure the check:

<module name="TodoComment"/>
        

To configure the check for comments that contain WARNING:

<module name="TodoComment">
    <property name="format" value="WARNING"/>
</module>
        

Package

com.puppycrawl.tools.checkstyle.checks

Parent Module

TreeWalker

Description

A FileSetCheck that ensures the correct translation of code by checking property files for consistency regarding their keys. Two property files describing one and the same context are consistent if they contain the same keys.

Consider the following properties file in the same directory:

#messages.properties
hello=Hello
cancel=Cancel

#messages_de.properties
hell=Hallo
ok=OK
        

The Translation check will find the typo in the german hello key, the missing ok key in the default resource file and the missing cancel key in the german resource file:

messages_de.properties: Key 'hello' missing.
messages_de.properties: Key 'cancel' missing.
messages.properties: Key 'hell' missing.
messages.properties: Key 'ok' missing.
        

Properties

Example

To configure the check:

<module name="Translation"/>
        

Package

com.puppycrawl.tools.checkstyle.checks

Parent Module

Checker

Description

Checks for uncommented main() methods (debugging leftovers).

Rationale: A main() method is often used for debug puposes. When debugging is finished, developers often forget to remove the method, which changes the API and increases the size of the resulting class/jar file. With the exception of the real program entry points, all main() methods should be removed/commented out of the sources.

Properties

Examples

To configure the check:

<module name="UncommentedMain"/>
        

To configure the check to allow main method for all classes with "Main" name:

<module name="UncommentedMain">
    <property name="excludedClasses" value="\.Main$"/>
</module>
        

Package

com.puppycrawl.tools.checkstyle.checks

Parent Module

TreeWalker

Description

Checks that long constants are defined with an upper ell. That is ' L' and not 'l'. This is in accordance to the Java Language Specification, Section 3.10.1.

looks a lot like 1.

Examples

To configure the check:

<module name="UpperEll"/>
        

Package

com.puppycrawl.tools.checkstyle.checks

Parent Module

TreeWalker

Description

Checks the style of array type definitions. Some like Java-style: public static void main(String[] args) and some like C-style: public static void main(String args[])

Properties

Examples

To configure the check to enforce Java style:

<module name="ArrayTypeStyle"/>
        

To configure the check to enforce C style:

<module name="ArrayTypeStyle">
    <property name="javaStyle" value="false"/>
</module>
        

Package

com.puppycrawl.tools.checkstyle.checks

Parent Module

TreeWalker

Description

Check that method/constructor/catch block parameters are final. Interface and abstract methods are not checked - the final keyword does not make sense for interface and abstract method parameters as there is no code that could modify the parameter.

Rationale: Changing the value of parameters during the execution of the method's algorithm can be confusing and should be avoided. A great way to let the Java compiler prevent this coding style is to declare parameters final.

Properties

Examples

To configure the check to enforce final parameters for methods and constructors:

<module name="FinalParameters"/>
        

To configure the check to enforce final parameters only for constructors:

<module name="FinalParameters">
    <property name="tokens" value="CTOR_DEF"/>
</module>
        

Package

com.puppycrawl.tools.checkstyle.checks

Parent Module

TreeWalker

Description

Checks for restricted tokens beneath other tokens.

WARNING: This is a very powerful and flexible check, but, at the same time, it is low level and very implementation dependent because its results depend on the grammar we use to build abstract syntax trees. Thus we recomend using other checks when they provide the desired funcionality. All in all, this check just works on the level of an abstract tree and knows nothing about language structures.

Properties

Examples

Comparing this with null (i.e. this == null and this != null):

<module name="DescendantToken">
    <property name="tokens" value="EQUAL,NOT_EQUAL"/>
    <property name="limitedTokens" value="LITERAL_THIS,LITERAL_NULL"/>
    <property name="maximumNumber" value="1"/>
    <property name="maximumDepth" value="1"/>
    <property name="sumTokenCounts" value="true"/>
</module>
        

String literal equality check:

<module name="DescendantToken">
    <property name="tokens" value="EQUAL,NOT_EQUAL"/>
    <property name="limitedTokens" value="STRING_LITERAL"/>
    <property name="maximumNumber" value="0"/>
    <property name="maximumDepth" value="1"/>
</module>
        

Switch with no default:

<module name="DescendantToken">
    <property name="tokens" value="LITERAL_SWITCH"/>
    <property name="maximumDepth" value="2"/>
    <property name="limitedTokens" value="LITERAL_DEFAULT"/>
    <property name="minimumNumber" value="1"/>
</module>
        

Assert statement may have side effects (formatted for browser display):

<module name="DescendantToken">
    <property name="tokens" value="LITERAL_ASSERT"/>
    <property name="limitedTokens" value="ASSIGN,DEC,INC,POST_DEC,
        POST_INC,PLUS_ASSIGN,MINUS_ASSIGN,STAR_ASSIGN,DIV_ASSIGN,MOD_ASSIGN,
        BSR_ASSIGN,SR_ASSIGN,SL_ASSIGN,BAND_ASSIGN,BXOR_ASSIGN,BOR_ASSIGN,
        METHOD_CALL"/>
    <property name="maximumNumber" value="0"/>
</module>
        

Initialiser in for performs no setup (use while instead?):

<module name="DescendantToken">
    <property name="tokens" value="FOR_INIT"/>
    <property name="limitedTokens" value="EXPR"/>
    <property name="minimumNumber" value="1"/>
</module>
        

Condition in for performs no check:

<module name="DescendantToken">
    <property name="tokens" value="FOR_CONDITION"/>
    <property name="limitedTokens" value="EXPR"/>
    <property name="minimumNumber" value="1"/>
</module>
        

Switch within switch:

<module name="DescendantToken">
    <property name="tokens" value="LITERAL_SWITCH"/>
    <property name="limitedTokens" value="LITERAL_SWITCH"/>
    <property name="maximumNumber" value="0"/>
    <property name="minimumDepth" value="1"/>
</module>
        

Return from within a catch or finally block:

<module name="DescendantToken">
    <property name="tokens" value="LITERAL_FINALLY,LITERAL_CATCH"/>
    <property name="limitedTokens" value="LITERAL_RETURN"/>
    <property name="maximumNumber" value="0"/>
</module>
        

Try within catch or finally block:

<module name="DescendantToken">
    <property name="tokens" value="LITERAL_CATCH,LITERAL_FINALLY"/>
    <property name="limitedTokens" value="LITERAL_TRY"/>
    <property name="maximumNumber" value="0"/>
</module>
        

Too many cases within a switch:

<module name="DescendantToken">
    <property name="tokens" value="LITERAL_SWITCH"/>
    <property name="limitedTokens" value="LITERAL_CASE"/>
    <property name="maximumDepth" value="2"/>
    <property name="maximumNumber" value="10"/>
</module>
        

Too many local variables within a method:

<module name="DescendantToken">
    <property name="tokens" value="METHOD_DEF"/>
    <property name="limitedTokens" value="VARIABLE_DEF"/>
    <property name="maximumDepth" value="2"/>
    <property name="maximumNumber" value="10"/>
</module>
        

Too many returns from within a method:

<module name="DescendantToken">
    <property name="tokens" value="METHOD_DEF"/>
    <property name="limitedTokens" value="LITERAL_RETURN"/>
    <property name="maximumNumber" value="3"/>
</module>
        

Too many fields within an interface:

<module name="DescendantToken">
    <property name="tokens" value="INTERFACE_DEF"/>
    <property name="limitedTokens" value="VARIABLE_DEF"/>
    <property name="maximumDepth" value="2"/>
    <property name="maximumNumber" value="0"/>
</module>
        

Limit the number of exceptions a method can throw:

<module name="DescendantToken">
    <property name="tokens" value="LITERAL_THROWS"/>
    <property name="limitedTokens" value="IDENT"/>
    <property name="maximumNumber" value="1"/>
</module>
        

Limit the number of expressions in a method:

<module name="DescendantToken">
    <property name="tokens" value="METHOD_DEF"/>
    <property name="limitedTokens" value="EXPR"/>
    <property name="maximumNumber" value="200"/>
</module>
        

Disallow empty statements:

<module name="DescendantToken">
    <property name="tokens" value="EMPTY_STAT"/>
    <property name="limitedTokens" value="EMPTY_STAT"/>
    <property name="maximumNumber" value="0"/>
    <property name="maximumDepth" value="0"/>
    <property name="maximumMessage"
        value="Empty statement is not allowed."/>
</module>
        

Too many fields within a class:

<module name="DescendantToken">
    <property name="tokens" value="CLASS_DEF"/>
    <property name="limitedTokens" value="VARIABLE_DEF"/>
    <property name="maximumDepth" value="2"/>
    <property name="maximumNumber" value="10"/>
</module>
        

Package

com.puppycrawl.tools.checkstyle.checks

Parent Module

TreeWalker

Description

Checks correct indentation of Java Code.

The basic idea behind this is that while pretty printers are sometimes convienent for bulk reformats of legacy code, they often either aren't configurable enough or just can't anticipate how format should be done. Sometimes this is personal preference, other times it is practical experience. In any case, this check should just ensure that a minimal set of indentation rules are followed.

Properties

Examples

To configure the check:

<module name="Indentation"/>
        

To configure the check to enforce indentation style recommended by Sun:

<module name="Indentation">
    <property name="caseIndent" value="0"/>
</module>
        

Package

com.puppycrawl.tools.checkstyle.checks.indentation

Parent Module

TreeWalker

Description

The check to ensure that requires that comments be the only thing on a line. For the case of // comments that means that the only thing that should precede it is whitespace. It doesn't check comments if they do not end line, i.e. it accept the following: Thread.sleep( 10 <some comment here> ); Format property is intended to deal with the "} // while" example.

Rationale: Steve McConnel in "Code Complete" suggests that endline comments are a bad practice. An end line comment would be one that is on the same line as actual code. For example:

a = b + c;      // Some insightful comment
d = e / f;        // Another comment for this line
        

Quoting "Code Complete" for the justfication:

• "The comments have to be aligned so that they do not interfere with the visual structure of the code. If you don't align them neatly, they'll make your listing look like it's been through a washing machine."
• "Endline comments tend to be hard to format...It takes time to align them. Such time is not spent learning more about the code; it's dedicated solely to the tedious task of pressing the spacebar or tab key."
• "Endline comments are also hard to maintain. If the code on any line containing an endline comment grows, it bumps the comment farther out, and all the other endline comments will have to bumped out to match. Styles that are hard to maintain aren't maintained...."
• "Endline comments also tend to be cryptic. The right side of the line doesn't offer much room and the desire to keep the comment on one line means the comment must be short. Work then goes into making the line as short as possible instead of as clear as possible. The comment usually ends up as cryptic as possible...."
• "A systemic problem with endline comments is that it's hard to write a meaningful comment for one line of code. Most endline comments just repeat the line of code, which hurts more than it helps."

His comments on being hard to maintain when the size of the line changes are even more important in the age of automated refactorings.

Properties

Examples

To configure the check:

<module name="TrailingComment"/>
        

To configure the check so it enforces only comment on a line:

<module name="TrailingComment">
    <property name="format" value="^\\s*$"/>
 </module>
        

Package

com.puppycrawl.tools.checkstyle.checks.indentation

Parent Module

TreeWalker

Description

A check that makes sure that a specified pattern exists, exists less than a set number of times, or does not exist in the file.

This check combines all the functionality provided by RegexpHeader, GenericIllegalRegexp and RequiredRegexp, except supplying the regular expression from a file.

It differs from them in that it works in multiline mode. It's regular expression can span multiple lines and it checks this against the whole file at once. The others work in singleline mode. Their single or multiple regular expressions can only span one line. They check each of these against each line in the file in turn.

Note: Because of the different mode of operation there may be some changes in the regular expressions used to achieve a particular end.

In multiline mode...

• ^ means beginning of a line, as oposed to beginning of input.
• For beginning of input use \A.
• $ means end of a line, as oposed to end of input.
• For end of input use \Z.
• Each line in the file is terminated with a newline character.

Note: Not all regexp engines are created equal. Some provide extra functions that others do not and some elements of the syntax may vary. This check makes use of the java.util.regex package, please check its documentation for details of how to construct a regular expression to achive a particular goal.

Note: When entering a regular expression as a parameter in the xml config file you must also take into account the xml rules. e.g. if you want to match a < symbol you need to enter &lt;. The regular expression should be entered on one line.

Properties

Examples

The following examples are mainly copied from the other 3 checks mentioned above, to show how the same results can be acheived using this check in place of them.

To use like RequiredRegexp :

An example of how to configure the check to make sure a copyright statement is included in the file:

The statement.

// This code is copyrighted
        

The check.

<module name="Regexp">
   <property name="format" value="// This code is copyrighted"/>
</module>
        

Your statement may be multiline.

// This code is copyrighted
// (c) MyCompany
        

Then the check would be.

<module name="Regexp">
   <property name="format" value="// This code is copyrighted\n// \(c\) MyCompany"/>
</module>
        

Note: To search for parentheses () in a regular expression you must escape them like \(\). This is required by the regexp engine, otherwise it will think they are special instruction characters.

And to make sure it appears only once:

<module name="Regexp">
   <property name="format" value="// This code is copyrighted\n// \(c\) MyCompany"/>
   <property name="duplicateLimit" value="0"/>
</module>
        

It can also be useful to attach a meaningful message to the check:

<module name="Regexp">
   <property name="format" value="// This code is copyrighted\n// \(c\) MyCompany"/>
   <property name="message" value="Copyright"/>
</module>
        

To use like GenericIllegalRegexp :

An example of how to configure the check to make sure there are no calls to System.out.println:

<module name="Regexp">
    <!-- . matches any character, so we need to escape it and use \. to match dots. -->
    <property name="format" value="System\.out\.println"/>
    <property name="illegalPattern" value="true"/>
</module>
        

You may want to make the above check ignore comments, like this:

<module name="Regexp">
    <property name="format" value="System\.out\.println"/>
    <property name="illegalPattern" value="true"/>
    <property name="ignoreComments" value="true"/>
</module>
        

An example of how to configure the check to find trailing whitespace at the end of a line:

<module name="Regexp">
    <property name="format" value="[ \t]+$"/>
    <property name="illegalPattern" value="true"/>
    <property name="message" value="Trailing whitespace"/>
</module>
        

Note: The difference between this and the example given for GenericIllegalRegexp is necessary because \s and $ both match the newline character ("\n").

An example of how to configure the check to find case-insensitive occurrences of "debug":

<module name="Regexp">
    <property name="format" value="(?i)debug"/>
    <property name="illegalPattern" value="true"/>
</module>
        

Note: The (?i) at the beginning of the regular expression tells the regexp engine to ignore the case.

There is also a feature to limit the number of errors reported. When the limit is reached the check aborts with a message reporting that the limit has been reached. The default limit setting is 100, but this can be change as shown in the following example.

<module name="Regexp">
    <property name="format" value="(?i)debug"/>
    <property name="illegalPattern" value="true"/>
    <property name="errorLimit" value="1000"/>
</module>
        

To use like RegexpHeader :

To configure the check to verify that each file starts with the following multiline header.

Note the following:

• \A means the start of the file.
• The date can be any 4 digit number.

// Copyright (C) 2004 MyCompany
// All rights reserved
        

<module name="Regexp">
  <property
    name="format"
    value="\A// Copyright \(C\) \d\d\d\d MyCompany\n// All rights reserved"/>
</module>
        

A more complex example. Note how the import and javadoc multilines are handled, there can be any number of them.

///////////////////////////////////////////////////////////////////////
// checkstyle:
// Checks Java source code for adherence to a set of rules.
// Copyright (C) 2004  Oliver Burn
// Last modification by $Author A.N.Other$
///////////////////////////////////////////////////////////////////////

package com.puppycrawl.checkstyle;

import java.util.thing1;
import java.util.thing2;
import java.util.thing3;

/**
 * javadoc line 1
 * javadoc line 2
 * javadoc line 3
 */
        

<module name="Regexp">
  <property
    name="format"
    value="\A/{71}\n// checkstyle:\n// Checks Java source code for
    adherence to a set of rules\.\n// Copyright \(C\) \d\d\d\d  Oliver Burn\n
    // Last modification by \$Author.*\$\n/{71}\n\npackage [\w\.]*;\n\n
    (import [\w\.]*;\n)*\n/\*\*\n( \*[^/]*\n)* \*/"/>
</module>
        

More examples:

The next 2 examples deal with the following example java source file:

/*
 * PID.java
 *
 * Copyright (c) 2001 ACME
 * 123 Some St.
 * Somewhere.
 *
 * This software is the confidential and proprietary information of ACME.
 * ("Confidential Information"). You shall not disclose such
 * Confidential Information and shall use it only in accordance with
 * the terms of the license agreement you entered into with ACME.
 *
 * $Log: config_misc.xml,v $
 * Revision 1.7  2007/01/16 12:16:35  oburn
 * Removing all reference to mailing lists
 *
 * Revision 1.6  2005/12/25 16:13:10  o_sukhodolsky
 * Fix for rfe 1248106 (TYPECAST is now accepted by NoWhitespaceAfter)
 *
 * Fix for rfe 953266 (thanks to Paul Guyot (pguyot) for submitting patch)
 * IllegalType can be configured to accept some abstract classes which
 * matches to regexp of illegal type names (property legalAbstractClassNames)
 *
 * TrailingComment now can be configured to accept some trailing comments
 * (such as NOI18N) (property legalComment, rfe 1385344).
 *
 * Revision 1.5  2005/11/06 11:54:12  oburn
 * Incorporate excellent patch [ 1344344 ] Consolidation of regexp checks.
 *
 * Revision 1.3.8.1  2005/10/11 14:26:32  someone
 * Fix for bug 251.  The broken bit is fixed
 */

package com.acme.tools;

import com.acme.thing1;
import com.acme.thing2;
import com.acme.thing3;

/**
 *
 * <P>
 *   <I>This software is the confidential and proprietary information of
 *   ACME (<B>"Confidential Information"</B>). You shall not
 *   disclose such Confidential Information and shall use it only in
 *   accordance with the terms of the license agreement you entered into
 *   with ACME.</I>
 * </P>
 *
 * &#169; copyright 2002 ACME
 *
 * @author   Some Body
 */
public class PID extends StateMachine implements WebObject.Constants {

    /** javadoc. */
    public static final int A_SETPOINT = 1;
    .
    .
    .
} // class PID
        

This checks for the presence of the header, the first 16 lines.

Note the following:

• Line 2 and 13 contain the file name. These are checked to make sure they are the same, and that they match the class name.
• The date can be any 4 digit number.

<module name="Regexp">
        <property
                name="format"
                value="\A/\*\n \* (\w*)\.java\n \*\n \* Copyright \(c\)
                \d\d\d\d ACME\n \* 123 Some St\.\n \* Somewhere\.\n \*\n
                \* This software is the confidential and proprietary information
                of ACME\.\n \* \("Confidential Information"\)\. You
                shall not disclose such\n \* Confidential Information and shall
                use it only in accordance with\n \* the terms of the license
                agreement you entered into with ACME\.\n \*\n
                \* \$Log: config_misc.xml,v $
                \* \Revision 1.7  2007/01/16 12:16:35  oburn
                \* \Removing all reference to mailing lists
                \* \
                \* \Revision 1.6  2005/12/25 16:13:10  o_sukhodolsky
                \* \Fix for rfe 1248106 (TYPECAST is now accepted by NoWhitespaceAfter)
                \* \
                \* \Fix for rfe 953266 (thanks to Paul Guyot (pguyot) for submitting patch)
                \* \IllegalType can be configured to accept some abstract classes which
                \* \matches to regexp of illegal type names (property legalAbstractClassNames)
                \* \
                \* \TrailingComment now can be configured to accept some trailing comments
                \* \(such as NOI18N) (property legalComment, rfe 1385344).
                \* \
                \* \Revision 1.5  2005/11/06 11:54:12  oburn
                \* \Incorporate excellent patch [ 1344344 ] Consolidation of regexp checks.
                \* \\n(.*\n)*([\w|\s]*( class | interface )\1)"/>
        <property name="message" value="Correct header not found"/>
</module>
        

This checks for the presence of a copyright notice within the class javadoc, lines 24 to 37.

<module name="Regexp">
        <property
                name="format"
                value="(/\*\*\n)( \*.*\n)*( \* &lt;P&gt;\n \*   &lt;I&gt;
                This software is the confidential and proprietary information of\n
                \*   ACME \(&lt;B&gt;&quot;Confidential Information&quot;&lt;/B&gt;
                \)\. You shall not\n \*   disclose such Confidential Information
                and shall use it only in\n \*   accordance with the terms of the
                license agreement you entered into\n \*   with ACME\.&lt;/I&gt;\n
                 \* &lt;/P&gt;\n \*\n \* &#169; copyright \d\d\d\d ACME\n
                  \*\n \* @author .*)(\n\s\*.*)*/\n[\w|\s]*( class | interface )"/>
        <property name="message" value="Copyright in class/interface Javadoc"/>
        <property name="duplicateLimit" value="0"/>
</module>
        

Note: To search for things that mean something in xml, like < you need to escape them like &lt;. This is required so the xml parser does not act on them, but instead passes the correct character to the regexp engine.

Package

com.puppycrawl.tools.checkstyle.checks

Parent Module

TreeWalker

Description

Checks that the outer type name and the file name match. For example, the class Foo must be in a file named Foo.java.

Properties

None.

Examples

To configure the check:

<module name="OuterTypeFilename"/>
        

Package

com.puppycrawl.tools.checkstyle.checks

Parent Module

TreeWalker