Checkstyle 5.5

##### About

- Checkstyle
- Release Notes

##### Documentation

- Configuration
  - Property Types
- Running
  - Ant Task
  - Command Line
- Available Checks
- Standard Checks
  - Annotations
  - Block Checks
  - Class Design
  - Coding
  - Duplicate Code
  - Headers
  - Imports
  - Javadoc Comments
  - Metrics
  - Miscellaneous
  - Modifiers
  - Naming Conventions
  - Regexp
  - Size Violations
  - Whitespace
- Extending Checkstyle
  - Writing checks
  - Writing filters
  - Writing listeners

##### Developers

- Javadoc
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- Contributing

##### Project Documentation

- Project Information
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## Header

### Description

Checks that a source file begins with a specified header. Property `headerFile` specifies a file that contains the required header. Alternatively, the header specification can be set directly in the `header` property without the need for an external file.

Property `ignoreLines` specifies the line numbers to ignore when matching lines in a header file. This property is very useful for supporting headers that contain copyright dates. For example, consider the following header:

    line 1: ////////////////////////////////////////////////////////////////////
    line 2: // checkstyle:
    line 3: // Checks Java source code for adherence to a set of rules.
    line 4: // Copyright (C) 2002  Oliver Burn
    line 5: ////////////////////////////////////////////////////////////////////

Since the year information will change over time, you can tell Checkstyle to ignore line 4 by setting property `ignoreLines` to `4`.

### Properties

name | description | type | default value
--- | --- | --- | ---
headerFile | name of the file containing the required header | string | `null`
charset | character encoding to use when reading the headerFile | string | the charset property of the parent Checker module
header | the required header specified inline. Individual header lines must be separated by the string `"\n"` (even on platforms with a different line separator), see examples below. | string | `null`
ignoreLines | line numbers to ignore | list of integers | `{}`
fileExtensions | file type extension of files to process | String Set | `{}`

### Example

To configure the check to use header file `"java.header"` and ignore lines `2`, `3`, and `4` and only process Java files:

    <module name="Header">
        <property name="headerFile" value="java.header"/>
        <property name="ignoreLines" value="2, 3, 4"/>
        <property name="fileExtensions" value="java"/>
    </module>

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

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

without the need for an external header file:

    <module name="Header">
        <property name="header"
                  value="// Copyright (C) 2004 MyCompany\n// All rights reserved"/>
    </module>

### Package

com.puppycrawl.tools.checkstyle.checks.header

### Parent Module

Checker

## RegexpHeader

### Description

Checks the header of a source file against a header that contains a regular expression 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).

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.

### Properties

name | description | type | default value
--- | --- | --- | ---
headerFile | name of the file containing the required header | string | `null`
charset | character encoding to use when reading the headerFile | string | the charset property of the parent Checker module
header | the required header specified inline. Individual header lines must be separated by the string `"\n"` (even on platforms with a different line separator), and regular expressions must not span multiple lines. | string | `null`
multiLines | line numbers to repeat (zero or more times) | list of integers | `{}`
fileExtensions | file type extension of files to process | String Set | `{}`

### Example

To configure the check to use header file `"java.header"` and `10` and `13` muli-lines:

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

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

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

### Package

com.puppycrawl.tools.checkstyle.checks.header

### Parent Module

Checker