Since Checkstyle 6.9


Checks the header of a source file against a header that contains a pattern for each line of the source header.

Rationale: In some projects checking against a fixed header is not sufficient, e.g. the header might require a copyright line where the year information is not static.

For example, consider the following header:

line  1: ^/{71}$
line  2: ^// checkstyle:$
line  3: ^// Checks Java source code for adherence to a set of rules\.$
line  4: ^// Copyright \(C\) \d\d\d\d  Oliver Burn$
line  5: ^// Last modification by \$Author.*\$$
line  6: ^/{71}$
line  7:
line  8: ^package
line  9:
line 10: ^import
line 11:
line 12: ^/\*\*
line 13: ^ \*([^/]|$)
line 14: ^ \*/

Lines 1 and 6 demonstrate a more compact notation for 71 '/' characters. Line 4 enforces that the copyright notice includes a four digit year. Line 5 is an example how to enforce revision control keywords in a file header. Lines 12-14 is a template for javadoc (line 13 is so complicated to remove conflict with and of javadoc comment). Lines 7, 9 and 11 will be treated as '^$' and will forcefully expect the line to be empty.

Different programming languages have different comment syntax rules, but all of them start a comment with a non-word character. Hence, you can often use the non-word character class to abstract away the concrete comment syntax and allow checking the header for different languages with a single header definition. For example, consider the following header specification (note that this is not the full Apache license header):

line 1: ^#!
line 2: ^<\?xml.*>$
line 3: ^\W*$
line 4: ^\W*Copyright 2006 The Apache Software Foundation or its licensors, as applicable\.$
line 5: ^\W*Licensed under the Apache License, Version 2\.0 \(the "License"\);$
line 6: ^\W*$

Lines 1 and 2 leave room for technical header lines, e.g. the "#!/bin/sh" line in Unix shell scripts, or the XML file header of XML files. Set the multiline property to "1, 2" so these lines can be ignored for file types where they do no apply. Lines 3 through 6 define the actual header content. Note how lines 2, 4 and 5 use escapes for characters that have special regexp semantics.

In default configuration, if header is not specified, the default value of header is set to null and the check does not rise any violations.


name description type default value since
charset Specify the character encoding to use when reading the headerFile. String the charset property of the parent <a href="">Checker</a> module 5.0
fileExtensions Specify the file extensions of the files to process. String[] all files 6.9
header Define the required header specified inline. Individual header lines must be separated by the string "\n" (even on platforms with a different line separator). For header lines containing "\n\n" checkstyle will forcefully expect an empty line to exist. See examples below. Regular expressions must not span multiple lines. String null 5.0
headerFile Specify the name of the file containing the required header. URI null 3.2
multiLines Specify the line numbers to repeat (zero or more times). int[] {} 3.4


To configure the check such that no violations arise. Default values of properties are used.

<module name="Checker">
  <module name="RegexpHeader"/>

To configure the check to use header file "config/java.header" and 10 and 13 multi-lines:

<module name="Checker">
  <module name="RegexpHeader">
    <property name="headerFile" value="config/java.header"/>
    <property name="multiLines" value="10, 13"/>

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

^// Copyright \(C\) (\d\d\d\d -)? 2004 MyCompany$
^// All rights reserved$

without the need for an external header file:

<module name="Checker">
  <module name="RegexpHeader">
      value="^// Copyright \(C\) (\d\d\d\d -)? 2004 MyCompany$
        \n^// All rights reserved$"/>

For regex containing "\n\n"

<module name="Checker">
  <module name="RegexpHeader">
      value="^package .*\n\n.*"/>

"\n\n" will be treated as '^$' and will forcefully expect the line to be empty. For example -

package com.some.package;
public class ThisWillFail { }

would fail for the regex above. Expected -

package com.some.package;

public class ThisWillPass { }

Note: ignoreLines property has been removed from this check to simplify it. To make some line optional use "^.*$" regexp for this line.

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.


Parent Module