Checkstyle - Java Code Quality Tool

Checkstyle is a tool that ensures adherence to a code standard or a set of best practices.

The latest release version can be found at GitHub releases or at Maven repo.

Documentation is available in HTML format, see Checkstyle checks.

Table of Contents

• Quick Start
• Contributing
• Feedback and Support
• Javadoc
• Sponsor Checkstyle
• Licensing

Quick Start

• Download our Latest Release from GitHub or add Checkstyle to your build from Maven Central.
• Read our Documentation for usage and configuration.

$ cat config.xml
<?xml version="1.0"?>
<!DOCTYPE module PUBLIC
          "-//Puppy Crawl//DTD Check Configuration 1.3//EN"
          "https://checkstyle.org/dtds/configuration_1_3.dtd">
<module name="Checker">
  <module name="TreeWalker">
    <module name="FallThrough"/>
  </module>
</module>

$ cat Test.java
class Test {
  public void foo() {
    int i = 0;
    while (i >= 0) {
      switch (i) {
        case 1:
        case 2:
          i++;
        case 3: // violation 'fall from previous branch of the switch'
          i++;
      }
    }
  }
}

$ java -jar checkstyle-10.18.1-all.jar -c config.xml Test.java
Starting audit...
[ERROR] Test.java:9:9: Fall through from previous branch of switch statement [FallThrough]
Audit done.
Checkstyle ends with 1 errors.

Contributing

Thanks for your interest in contributing to CheckStyle! Please see the Contribution Guidelines for information on how to contribute to the project. This includes creating issues, submitting pull requests, and setting up your development environment.

Build Instructions

Please see the Build Instructions for information on how to build the project.

Feedback and Support

• Visit our Discussions Page, where you can ask questions and discuss the project with other users and contributors. This is our preferred method of communication for topics like usage and configuration questions, debugging, and other feedback.
• Stack Overflow is another place to ask questions about Checkstyle usage.
• If you are interested in contributing to the project, you can join our Discord Contributors Chat with invite link.
• Our Google Groups Forum is a mailing list for discussion and support; however, we may be slow to respond there.

Javadoc

Take a look at our javadoc to see our API documentation.

Sponsor Checkstyle

Checkstyle is an open-source project that is developed and maintained by volunteers. If you find Checkstyle useful, please consider sponsoring the project. Your support helps us to maintain and improve Checkstyle.

• Liberapay
• OpenCollective

Licensing

Checkstyle is licensed under the GNU LGPL v2.1 License. Checkstyle uses libraries:

• ANTLR
• Apache Commons
• Google Guava
• Picocli

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