Class UncommentedMainCheck

  • All Implemented Interfaces:
    Configurable, Contextualizable

    public class UncommentedMainCheck
    extends AbstractCheck

    Detects uncommented main methods.

    Rationale: A main method is often used for debugging purposes. When debugging is finished, developers often forget to remove the method, which changes the API and increases the size of the resulting class or JAR file. Except for the real program entry points, all main methods should be removed or commented out of the sources.

    • Property excludedClasses - Specify pattern for qualified names of classes which are allowed to have a main method. Type is java.util.regex.Pattern. Default value is "^$".

    To configure the check:

     <module name="UncommentedMain"/>
     

    Example:

     public class Game {
        public static void main(String... args){}   // violation
     }
    
     public class Main {
        public static void main(String[] args){}   // violation
     }
    
     public class Launch {
        //public static void main(String[] args){} // OK
     }
    
     public class Start {
        public void main(){}                       // OK
     }
    
     public record MyRecord1 {
        public void main(){}                       // violation
     }
    
     public record MyRecord2 {
        //public void main(){}                       // OK
     }
    
     

    To configure the check to allow the main method for all classes with "Main" name:

     <module name="UncommentedMain">
       <property name="excludedClasses" value="\.Main$"/>
     </module>
     

    Example:

     public class Game {
        public static void main(String... args){}   // violation
     }
    
     public class Main {
        public static void main(String[] args){}   // OK
     }
    
     public class Launch {
        //public static void main(String[] args){} // OK
     }
    
     public class Start {
        public void main(){}                       // OK
     }
    
     public record MyRecord1 {
        public void main(){}                       // OK
     }
    
     

    Parent is com.puppycrawl.tools.checkstyle.TreeWalker

    Violation Message Keys:

    • uncommented.main
    Since:
    3.2
    • Method Detail

      • setExcludedClasses

        public void setExcludedClasses​(Pattern excludedClasses)
        Setter to specify pattern for qualified names of classes which are allowed to have a main method.
        Parameters:
        excludedClasses - a pattern
      • getAcceptableTokens

        public int[] getAcceptableTokens()
        Description copied from class: AbstractCheck
        The configurable token set. Used to protect Checks against malicious users who specify an unacceptable token set in the configuration file. The default implementation returns the check's default tokens.
        Specified by:
        getAcceptableTokens in class AbstractCheck
        Returns:
        the token set this check is designed for.
        See Also:
        TokenTypes
      • beginTree

        public void beginTree​(DetailAST rootAST)
        Description copied from class: AbstractCheck
        Called before the starting to process a tree. Ideal place to initialize information that is to be collected whilst processing a tree.
        Overrides:
        beginTree in class AbstractCheck
        Parameters:
        rootAST - the root of the tree
      • visitPackageDef

        private void visitPackageDef​(DetailAST packageDef)
        Sets current package.
        Parameters:
        packageDef - node for package definition
      • visitClassOrRecordDef

        private void visitClassOrRecordDef​(DetailAST classOrRecordDef)
        If not inner class then change current class name.
        Parameters:
        classOrRecordDef - node for class or record definition
      • visitMethodDef

        private void visitMethodDef​(DetailAST method)
        Checks method definition if this is public static void main(String[]).
        Parameters:
        method - method definition node
      • checkClassName

        private boolean checkClassName()
        Checks that current class is not excluded.
        Returns:
        true if check passed, false otherwise
      • checkName

        private static boolean checkName​(DetailAST method)
        Checks that method name is @quot;main@quot;.
        Parameters:
        method - the METHOD_DEF node
        Returns:
        true if check passed, false otherwise
      • checkModifiers

        private static boolean checkModifiers​(DetailAST method)
        Checks that method has final and static modifiers.
        Parameters:
        method - the METHOD_DEF node
        Returns:
        true if check passed, false otherwise
      • checkType

        private static boolean checkType​(DetailAST method)
        Checks that return type is void.
        Parameters:
        method - the METHOD_DEF node
        Returns:
        true if check passed, false otherwise
      • checkParams

        private static boolean checkParams​(DetailAST method)
        Checks that method has only String[] or only String... param.
        Parameters:
        method - the METHOD_DEF node
        Returns:
        true if check passed, false otherwise
      • isStringType

        private static boolean isStringType​(DetailAST typeAst)
        Whether the type is java.lang.String.
        Parameters:
        typeAst - the type to check.
        Returns:
        true, if the type is java.lang.String.