MutableExceptionCheck (checkstyle 9.3 API)

java.lang.Object
- com.puppycrawl.tools.checkstyle.api.AutomaticBean
- - com.puppycrawl.tools.checkstyle.api.AbstractViolationReporter
  - - com.puppycrawl.tools.checkstyle.api.AbstractCheck
    - - com.puppycrawl.tools.checkstyle.checks.design.MutableExceptionCheck

All Implemented Interfaces:

Configurable, Contextualizable
```
public final class MutableExceptionCheck
extends AbstractCheck
```
Ensures that exception classes (classes with names conforming to some pattern and explicitly extending classes with names conforming to other pattern) are immutable, that is, that they have only final fields.

The current algorithm is very simple: it checks that all members of exception are final. The user can still mutate an exception's instance (e.g. Throwable has a method called setStackTrace which changes the exception's stack trace). But, at least, all information provided by this exception type is unchangeable.

Rationale: Exception instances should represent an error condition. Having non final fields not only allows the state to be modified by accident and therefore mask the original condition but also allows developers to accidentally forget to set the initial state. In both cases, code catching the exception could draw incorrect conclusions based on the state.
- Property format - Specify pattern for exception class names. Type is java.util.regex.Pattern. Default value is "^.*Exception$|^.*Error$|^.*Throwable$".
- Property extendedClassNameFormat - Specify pattern for extended class names. Type is java.util.regex.Pattern. Default value is "^.*Exception$|^.*Error$|^.*Throwable$".
To configure the check:
```
 <module name="MutableException"/>
 
```
Parent is com.puppycrawl.tools.checkstyle.TreeWalker

Violation Message Keys:
- mutable.exception
Since:

3.2

Nested Class Summary
- Nested classes/interfaces inherited from class com.puppycrawl.tools.checkstyle.api.AutomaticBean
  AutomaticBean.OutputStreamOptions

Field Summary

Fields
Modifier and Type	Field and Description
`private boolean`	`checking` Should we check current class or not.
`private java.util.Deque<java.lang.Boolean>`	`checkingStack` Stack of checking information for classes.
`private static java.lang.String`	`DEFAULT_FORMAT` Default value for format and extendedClassNameFormat properties.
`private java.util.regex.Pattern`	`extendedClassNameFormat` Specify pattern for extended class names.
`private java.util.regex.Pattern`	`format` Specify pattern for exception class names.
`static java.lang.String`	`MSG_KEY` A key is pointing to the warning message text in "messages.properties" file.

Constructor Summary

Constructors
Constructor and Description

MutableExceptionCheck()

Constructors
Constructor and Description
`MutableExceptionCheck()`

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`int[]`	`getAcceptableTokens()` The configurable token set.
`int[]`	`getDefaultTokens()` Returns the default token a check is interested in.
`int[]`	`getRequiredTokens()` The tokens that this check must be registered for.
`private boolean`	`isExtendedClassNamedAsException(DetailAST ast)` Checks that if extended class name conforms to specified format.
`private boolean`	`isNamedAsException(DetailAST ast)` Checks that a class name conforms to specified format.
`private void`	`leaveClassDef()` Called when we leave class definition.
`void`	`leaveToken(DetailAST ast)` Called after all the child nodes have been process.
`void`	`setExtendedClassNameFormat(java.util.regex.Pattern extendedClassNameFormat)` Setter to specify pattern for extended class names.
`void`	`setFormat(java.util.regex.Pattern pattern)` Setter to specify pattern for exception class names.
`private void`	`visitClassDef(DetailAST ast)` Called when we start processing class definition.
`void`	`visitToken(DetailAST ast)` Called to process a token.
`private void`	`visitVariableDef(DetailAST ast)` Checks variable definition.

Methods inherited from class com.puppycrawl.tools.checkstyle.api.AbstractCheck
beginTree, clearViolations, destroy, finishTree, getFileContents, getLine, getLineCodePoints, getLines, getTabWidth, getTokenNames, getViolations, init, isCommentNodesRequired, 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

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - MSG_KEY
```
public static final java.lang.String MSG_KEY
```
    A key is pointing to the warning message text in "messages.properties" file.
    
    See Also:
    
    Constant Field Values
  - DEFAULT_FORMAT
```
private static final java.lang.String DEFAULT_FORMAT
```
    Default value for format and extendedClassNameFormat properties.
    
    See Also:
    
    Constant Field Values
  - checkingStack
```
private final java.util.Deque<java.lang.Boolean> checkingStack
```
    Stack of checking information for classes.
  - extendedClassNameFormat
```
private java.util.regex.Pattern extendedClassNameFormat
```
    Specify pattern for extended class names.
  - checking
```
private boolean checking
```
    Should we check current class or not.
  - format
```
private java.util.regex.Pattern format
```
    Specify pattern for exception class names.
- Constructor Detail
  - MutableExceptionCheck
```
public MutableExceptionCheck()
```
- Method Detail
  - setExtendedClassNameFormat
```
public void setExtendedClassNameFormat(java.util.regex.Pattern extendedClassNameFormat)
```
    Setter to specify pattern for extended class names.
    
    Parameters:
    
    extendedClassNameFormat - a String value
  - setFormat
```
public void setFormat(java.util.regex.Pattern pattern)
```
    Setter to specify pattern for exception class names.
    
    Parameters:
    
    pattern - the new pattern
  - getDefaultTokens
```
public int[] getDefaultTokens()
```
    Description copied from class: AbstractCheck
    
    Returns the default token a check is interested in. Only used if the configuration for a check does not define the tokens.
    
    Specified by:
    
    getDefaultTokens in class AbstractCheck
    
    Returns:
    
    the default tokens
    
    See Also:
    
    TokenTypes
  - getRequiredTokens
```
public int[] getRequiredTokens()
```
    Description copied from class: AbstractCheck
    
    The tokens that this check must be registered for.
    
    Specified by:
    
    getRequiredTokens in class AbstractCheck
    
    Returns:
    
    the token set this must be registered for.
    
    See Also:
    
    TokenTypes
  - 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
  - visitToken
```
public void visitToken(DetailAST ast)
```
    Description copied from class: AbstractCheck
    
    Called to process a token.
    
    Overrides:
    
    visitToken in class AbstractCheck
    
    Parameters:
    
    ast - the token to process
  - leaveToken
```
public void leaveToken(DetailAST ast)
```
    Description copied from class: AbstractCheck
    
    Called after all the child nodes have been process.
    
    Overrides:
    
    leaveToken in class AbstractCheck
    
    Parameters:
    
    ast - the token leaving
  - visitClassDef
```
private void visitClassDef(DetailAST ast)
```
    Called when we start processing class definition.
    
    Parameters:
    
    ast - class definition node
  - leaveClassDef
```
private void leaveClassDef()
```
    Called when we leave class definition.
  - visitVariableDef
```
private void visitVariableDef(DetailAST ast)
```
    Checks variable definition.
    
    Parameters:
    
    ast - variable def node for check
  - isNamedAsException
```
private boolean isNamedAsException(DetailAST ast)
```
    Checks that a class name conforms to specified format.
    
    Parameters:
    
    ast - class definition node
    
    Returns:
    
    true if a class name conforms to specified format
  - isExtendedClassNamedAsException
```
private boolean isExtendedClassNamedAsException(DetailAST ast)
```
    Checks that if extended class name conforms to specified format.
    
    Parameters:
    
    ast - class definition node
    
    Returns:
    
    true if extended class name conforms to specified format

Class MutableExceptionCheck

Nested Class Summary

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

Field Summary

Constructor Summary

Method Summary

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

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

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

Methods inherited from class java.lang.Object

Field Detail

MSG_KEY

DEFAULT_FORMAT

checkingStack

extendedClassNameFormat

checking

format

Constructor Detail

MutableExceptionCheck

Method Detail

setExtendedClassNameFormat

setFormat

getDefaultTokens

getRequiredTokens

getAcceptableTokens

visitToken

leaveToken

visitClassDef

leaveClassDef

visitVariableDef

isNamedAsException

isExtendedClassNamedAsException