pmd/docs/index.md

---
title: Documentation Index
keywords: java
permalink: index.html
toc: false
summary: >
    Welcome to the documentation site for PMD and CPD! <br/><br/>


last_updated: October 2022
author: Jeff Jensen <jjensen@apache.org>, Andreas Dangel <andreas.dangel@adangel.org>,
        Clément Fournier <clement.fournier76@gmail.com>

additional_js:
 - assets/Shuffle-5.2.3/dist/shuffle.min.js
 - assets/jquery-ui-1.12.1/jquery-ui.min.js
 - js/shuffle.js
---



## 💡 Overview

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**PMD** is an extensible multilanguage static code analyzer. It finds common programming flaws like unused variables,
empty catch blocks, unnecessary object creation, and so forth. It's mainly concerned with **Java and
Apex**, but **supports 16 other languages**. It comes with **400+ built-in rules**. It can be
extended with custom rules. It uses JavaCC and Antlr to parse source files into abstract syntax trees
(AST) and runs rules against them to find violations. Rules can be written in Java or using a XPath query.

Currently, PMD supports Java, JavaScript, Salesforce.com Apex and Visualforce,
Kotlin, Swift, Modelica, PLSQL, Apache Velocity, JSP, WSDL, Maven POM, HTML, XML and XSL.
Scala is supported, but there are currently no Scala rules available.

Additionally, it includes **CPD**, the copy-paste-detector. CPD finds duplicated code in
Coco, C/C++, C#, Dart, Fortran, Gherkin, Go, Groovy, HTML, Java, JavaScript, JSP, Julia, Kotlin,
Lua, Matlab, Modelica, Objective-C, Perl, PHP, PLSQL, Python, Ruby, Salesforce.com Apex and
Visualforce, Scala, Swift, T-SQL, Typescript, Apache Velocity, WSDL, XML and XSL.

PMD features many **built-in checks** (in PMD lingo, *rules*), which are documented
for each language in our [Rule references](#shuffle-panel-rule-references). We
also support an extensive API to [**write your own rules**](#shuffle-panel-writing-rules),
which you can do either in Java or as a self-contained XPath query.

PMD is most useful when **integrated into your build process**. It can then be
used as a quality gate, to enforce a coding standard for your codebase. Among other
things, PMD can be run:
* As a [Maven goal](pmd_userdocs_tools_maven.html)
* As an [Ant task](pmd_userdocs_tools_ant.html)
* As a [Gradle task](pmd_userdocs_tools_gradle.html)
* As a [bld operation](pmd_userdocs_tools_bld.html)
* From [command-line](pmd_userdocs_installation.html#running-pmd-via-command-line)

**CPD**, the **copy-paste detector**, is also distributed with PMD. You can use it
in a variety of ways, which are [documented here](pmd_userdocs_cpd.html).

## 💾 Download

The latest release of PMD can be downloaded from our [Github releases page](https://github.com/pmd/pmd/releases/latest).

The Logo is available from the [Logo Project Page](pmd_projectdocs_logo.html).

## 📖 Documentation

The rest of this page exposes the contents of the documentation site thematically,
which you can further scope down using the blue filter buttons. To navigate the site,
you may also use the search bar in the top right, or the sidebar on the left.

## ✨ Contributors

This project follows the [all-contributors](https://github.com/all-contributors/all-contributors) specification.
Contributions of any kind welcome!

See [credits](pmd_projectdocs_credits.html) for the complete list.

<br/>




<div class="filter-options" id='grid-rule' >
      <button class="btn btn-primary" data-group="all">All</button>
      <button class="btn btn-primary" data-group="getting_started">Getting Started</button>
      <button class="btn btn-primary" data-group="userdocs">User documentation</button>
      <button class="btn btn-primary" data-group="extending">Extending PMD</button>
      <button class="btn btn-primary" data-group="contributing">Contributing</button>
</div>



<div id="grid" class="row">

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    {% include custom/shuffle_panel.html
       title="Getting started"
       tags="getting_started"
       datagroups='["getting_started"]'
       description="These pages summarize the gist of PMD usage to get you started quickly." %}


    {% include custom/shuffle_panel.html
       title="Rule references"
       tags="rule_references"
       datagroups='["userdocs"]'
       description="Pick your language to find out about the rule it supports."
       fa-icon="fa-database"
       titlemaker="page.language_name" %}

    {% include custom/shuffle_panel.html
       title="Writing rules"
       tags="userdocs,extending"
       datagroups='["userdocs", "extending", "contributing"]'
       description="These pages document the process of writing and testing custom rules and metrics for PMD."
    %}

    {% include custom/shuffle_panel.html
       title="Usage and configuration"
       tags="userdocs"
       except_tags="extending,tools"
       datagroups='["userdocs"]'
       fa-icon="fa-cog"
       description="Learn how to build effective and versatile rulesets."
    %}


    {% include custom/shuffle_panel.html
       title="Contributing"
       tags="devdocs"
       except_tags="extending"
       datagroups='["contributing"]'
       fa-style="fab"
       fa-icon="fa-github"
       description="If you'd like to help us build PMD, these topics may interest you. See you around!"
    %}



    {% include custom/shuffle_panel.html
       title="Tools and integrations"
       tags="tools"
       datagroups='["userdocs"]'
       description="These pages describe solutions that integrate PMD within your build process."
    %}

    {% include custom/shuffle_panel.html
       title="Major contributions"
       tags="devdocs,extending"
       datagroups='["contributing","extending"]'
       description=""
    %}

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    <div class="col-xs-6 col-sm-4 col-md-1 shuffle_sizer"></div>
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