checkstyle

checkstyle documentation

Version in Mega-Linter: 9.0
Visit Official Web Site
See How to configure checkstyle rules
- If custom sun_checks.xml config file is not found, sun_checks.xml will be used
See How to disable checkstyle rules in files
See Index of problems detected by checkstyle

Configuration in Mega-Linter

Enable checkstyle by adding JAVA_CHECKSTYLE in ENABLE_LINTERS variable
Disable checkstyle by adding JAVA_CHECKSTYLE in DISABLE_LINTERS variable

Variable	Description	Default value
JAVA_CHECKSTYLE_ARGUMENTS	User custom arguments to add in linter CLI call Ex: `-s --foo "bar"`
JAVA_CHECKSTYLE_FILTER_REGEX_INCLUDE	Custom regex including filter Ex: `(src\\|lib)`	Include every file
JAVA_CHECKSTYLE_FILTER_REGEX_EXCLUDE	Custom regex excluding filter Ex: `(test\\|examples)`	Exclude no file
JAVA_CHECKSTYLE_CLI_LINT_MODE	Override default CLI lint mode - `file`: Calls the linter for each file - `list_of_files`: Call the linter with the list of files as argument - `project`: Call the linter from the root of the project	`{linter.cli_lint_mode}`
JAVA_CHECKSTYLE_FILE_EXTENSIONS	Allowed file extensions. `"*"` matches any extension, `""` matches empty extension. Empty list excludes all files Ex: `[".py", ""]`	`[".java"]`
JAVA_CHECKSTYLE_FILE_NAMES_REGEX	File name regex filters. Regular expression list for filtering files by their base names using regex full match. Empty list includes all files Ex: `["Dockerfile(-.+)?", "Jenkinsfile"]`	Include every file
JAVA_CHECKSTYLE_PRE_COMMANDS	List of bash commands to run before the linter	None
JAVA_CHECKSTYLE_POST_COMMANDS	List of bash commands to run after the linter	None
JAVA_CHECKSTYLE_CONFIG_FILE	checkstyle configuration file name Use `LINTER_DEFAULT` to let the linter find it	`sun_checks.xml`
JAVA_CHECKSTYLE_RULES_PATH	Path where to find linter configuration file	Workspace folder, then Mega-Linter default rules
JAVA_CHECKSTYLE_DISABLE_ERRORS	Run linter but consider errors as warnings	`false`
JAVA_CHECKSTYLE_DISABLE_ERRORS_IF_LESS_THAN	Maximum number of errors allowed	`0`

IDE Integration

Use checkstyle in your favorite IDE to catch errors before Mega-Linter !

IDE	Extension Name	Install
Eclipse	eclipse-cs	Visit Web Site
IDEA	checkstyle-idea
Visual Studio Code	vscode-checkstyle

Mega-Linter Flavours

This linter is available in the following flavours

	Flavor	Description	Embedded linters	Info
	all	Default Mega-Linter Flavor	93
	java	Optimized for JAVA based projects	41

Behind the scenes

How are identified applicable files

File extensions: .java

How the linting is performed

checkstyle is called one time by identified file

Example calls

java -jar /usr/bin/checkstyle myfile.java

java -jar /usr/bin/checkstyle -c sun_checks.xml myfile.java

Help content

Usage: java [-options] class [args...]
           (to execute a class)
   or  java [-options] -jar jarfile [args...]
           (to execute a jar file)
where options include:
    -d32    use a 32-bit data model if available
    -d64    use a 64-bit data model if available
    -server    to select the "server" VM
                  The default VM is server,
                  because you are running on a server-class machine.


    -cp <class search path of directories and zip/jar files>
    -classpath <class search path of directories and zip/jar files>
                  A : separated list of directories, JAR archives,
                  and ZIP archives to search for class files.
    -D<name>=<value>
                  set a system property
    -verbose:[class|gc|jni]
                  enable verbose output
    -version      print product version and exit
    -version:<value>
                  Warning: this feature is deprecated and will be removed
                  in a future release.
                  require the specified version to run
    -showversion  print product version and continue
    -jre-restrict-search | -no-jre-restrict-search
                  Warning: this feature is deprecated and will be removed
                  in a future release.
                  include/exclude user private JREs in the version search
    -? -help      print this help message
    -X            print help on non-standard options
    -ea[:<packagename>...|:<classname>]
    -enableassertions[:<packagename>...|:<classname>]
                  enable assertions with specified granularity
    -da[:<packagename>...|:<classname>]
    -disableassertions[:<packagename>...|:<classname>]
                  disable assertions with specified granularity
    -esa | -enablesystemassertions
                  enable system assertions
    -dsa | -disablesystemassertions
                  disable system assertions
    -agentlib:<libname>[=<options>]
                  load native agent library <libname>, e.g. -agentlib:hprof
                  see also, -agentlib:jdwp=help and -agentlib:hprof=help
    -agentpath:<pathname>[=<options>]
                  load native agent library by full pathname
    -javaagent:<jarpath>[=<options>]
                  load Java programming language agent, see java.lang.instrument
    -splash:<imagepath>
                  show splash screen with specified image
See http://www.oracle.com/technetwork/java/javase/documentation/index.html for more details.

Installation on mega-linter Docker image

Dockerfile commands :

# Parent descriptor install
ENV JAVA_HOME=/usr/lib/jvm/java-1.8-openjdk
ENV PATH="$JAVA_HOME/bin:${PATH}"
# Linter install
RUN CHECKSTYLE_LATEST=$(curl -s https://api.github.com/repos/checkstyle/checkstyle/releases/latest \
        | grep browser_download_url \
        | grep ".jar" \
        | cut -d '"' -f 4) \
    && curl --retry 5 --retry-delay 5 -sSL $CHECKSTYLE_LATEST \
        --output /usr/bin/checkstyle

Example success log

Results of checkstyle linter (version 8.38)
See documentation on https://nvuillam.github.io/mega-linter/descriptors/java_checkstyle/
-----------------------------------------------

[SUCCESS] .automation/test/java/java_good_1.java
    Starting audit...
    Audit done.

Example error log

Results of checkstyle linter (version 8.38)
See documentation on https://nvuillam.github.io/mega-linter/descriptors/java_checkstyle/
-----------------------------------------------

[ERROR] .automation/test/java/java_bad_1.java
    Starting audit...
    [ERROR] .automation/test/java/java_bad_1.java:1:1: Utility classes should not have a public or default constructor. [HideUtilityClassConstructor]
    [ERROR] .automation/test/java/java_bad_1.java:1:7: Name 'java_bad_1' must match pattern '^[A-Z][a-zA-Z0-9]*$'. [TypeName]
    [ERROR] .automation/test/java/java_bad_1.java:2:1: '{' at column 1 should be on the previous line. [LeftCurly]
    [ERROR] .automation/test/java/java_bad_1.java:4:29: Parameter args should be final. [FinalParameters]
    [ERROR] .automation/test/java/java_bad_1.java:4:40: Array brackets at illegal position. [ArrayTypeStyle]
    [ERROR] .automation/test/java/java_bad_1.java:5:5: '{' at column 5 should be on the previous line. [LeftCurly]
    Audit done.
    Checkstyle ends with 6 errors.