Package com.github.sevntu.checkstyle.checks.design

Class ConstructorWithoutParamsCheck

  • All Implemented Interfaces:
    com.puppycrawl.tools.checkstyle.api.Configurable, com.puppycrawl.tools.checkstyle.api.Contextualizable
    public class ConstructorWithoutParamsCheck
extends com.puppycrawl.tools.checkstyle.api.AbstractCheck
    This check prohibits usage of parameterless constructors, including the default ones.

    Rationale: constructors of certain classes must always take arguments to properly instantiate objects. Exception classes are the primary example: their objects must contain enough info to find out why an exception occurred (see "Effective Java", item 63). Constructing an exception without a cause exception or an exception message leaves out such info and thus should be prohibited.

    This check prohibits classes which simple names match the RegExp defined in 'classNameFormat' property.

    Default configuration: 

             <module name="ConstructorWithoutParamsCheck">
           <property name="classNameFormat" value=".*Exception$"/>
           <property name="ignoredClassNameFormat" value="UnsupportedOperationException"/>
         </module>

    Examples: 

     // Assume a RegExp in classNameFormat catches example class names
 // the check can prohibit default constructors of built-in classes
 RuntimeException ex = new RuntimeException(); // violation expected

 // the check ignores classes which names match ignoredClassNameFormat
 // the default config ignores UnsupportedOperationException
 UnsupportedOperationException ex2 = new UnsupportedOperationException(); // no violation expected

 // the check allows constructors with empty arguments
 RuntimeException ex = new RuntimeException(""); // no violation expected

 // the check can prohibit default constructors of user-defined classes
 public class Clazz1 {
 }

 Clazz1 o1 = new Clazz1(); // violation expected

 // the check can prohibit  user-defined parameterless constructors
 public class Clazz2 {

   Clazz2() {
     foobar();
   }

 }

 Clazz2 o2 = new Clazz2(); // violation expected

    For more examples, see InputConstructorWithoutParamsCheck. For discussion, see the sevntu-checkstyle issue 412

    .
    Since:
    1.20.0
    Author:
    Sergey Dudoladov

    • Nested Class Summary

      • Nested classes/interfaces inherited from class com.puppycrawl.tools.checkstyle.api.AutomaticBean

        com.puppycrawl.tools.checkstyle.api.AutomaticBean.OutputStreamOptions

    • Field Summary

      Fields 
      Modifier and Type Field Description
      static String MSG_KEY
      This key points to the warning message in the "messages.properties" file.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      int[] getAcceptableTokens()  
      int[] getDefaultTokens()  
      int[] getRequiredTokens()  
      void setClassNameFormat​(String classNameFormat)
      Sets the classNameFormat based on the XML configuration value.
      void setIgnoredClassNameFormat​(String ignoredClassNameFormat)
      Sets the ignoredClassNameFormat based on the XML configuration value.
      void visitToken​(com.puppycrawl.tools.checkstyle.api.DetailAST ast)  

      • Methods inherited from class com.puppycrawl.tools.checkstyle.api.AbstractCheck

        beginTree, clearViolations, destroy, finishTree, getFileContents, getFilePath, getLine, getLineCodePoints, getLines, getTabWidth, getTokenNames, getViolations, init, isCommentNodesRequired, leaveToken, log, log, log, setFileContents, setTabWidth, setTokens

      • Methods inherited from class com.puppycrawl.tools.checkstyle.api.AbstractViolationReporter

        finishLocalSetup, getCustomMessages, getId, getMessageBundle, getSeverity, getSeverityLevel, setId, setSeverity

      • Methods inherited from class com.puppycrawl.tools.checkstyle.api.AutomaticBean

        configure, contextualize, getConfiguration, setupChild

    • Field Detail

      • MSG_KEY

        public static final String MSG_KEY
        This key points to the warning message in the "messages.properties" file.
        See Also:
        Constant Field Values

    • Constructor Detail

      • ConstructorWithoutParamsCheck

        public ConstructorWithoutParamsCheck()

    • Method Detail

      • setClassNameFormat

        public void setClassNameFormat​(String classNameFormat)
        Sets the classNameFormat based on the XML configuration value.
        Parameters:
        classNameFormat - the regexp pattern

      • setIgnoredClassNameFormat

        public void setIgnoredClassNameFormat​(String ignoredClassNameFormat)
        Sets the ignoredClassNameFormat based on the XML configuration value.
        Parameters:
        ignoredClassNameFormat - the regexp pattern

      • getDefaultTokens

        public int[] getDefaultTokens()
        Specified by:
        getDefaultTokens in class com.puppycrawl.tools.checkstyle.api.AbstractCheck

      • getRequiredTokens

        public int[] getRequiredTokens()
        Specified by:
        getRequiredTokens in class com.puppycrawl.tools.checkstyle.api.AbstractCheck

      • getAcceptableTokens

        public int[] getAcceptableTokens()
        Specified by:
        getAcceptableTokens in class com.puppycrawl.tools.checkstyle.api.AbstractCheck

      • visitToken

        public void visitToken​(com.puppycrawl.tools.checkstyle.api.DetailAST ast)
        Overrides:
        visitToken in class com.puppycrawl.tools.checkstyle.api.AbstractCheck