com.github.sevntu.checkstyle.checks.design

Class ForbidWildcardAsReturnTypeCheck

java.lang.Object

com.puppycrawl.tools.checkstyle.api.AutomaticBean

com.puppycrawl.tools.checkstyle.api.AbstractViolationReporter

com.puppycrawl.tools.checkstyle.api.AbstractCheck

com.github.sevntu.checkstyle.checks.design.ForbidWildcardAsReturnTypeCheck

All Implemented Interfaces:

com.puppycrawl.tools.checkstyle.api.Configurable, com.puppycrawl.tools.checkstyle.api.Contextualizable

public class ForbidWildcardAsReturnTypeCheck
extends com.puppycrawl.tools.checkstyle.api.AbstractCheck

Prevents using wildcards as return type of methods.

Joshua Bloch, "Effective Java (2nd edition)" Item 28: page 137 :

"Do not use wildcard types as return types. Rather than providing additional flexibility for your users, it would force them to use wildcard types in client code. Properly used, wildcard types are nearly invisible to users of a class. They cause methods to accept the parameters they should accept and reject those they should reject. If the user of a class has to think about wildcard types, there is probably something wrong with the class’s API." Attention: some JDK classes have public methods with "?"(wildcard) in return type so it might not always possible to avoid wildcards in return type, as they do not demand user to bother about it (invisible for user or method). So suppressions should be used.

Examples: JDK Collectors, so usage of methods that return wildcard could force user customizations over Collectors use wildcard in public methods

 // custom util method, wildcard come from Collectors.toList()
 public <T> Collector<T, ?, T> singleResult(Function<? super Iterable<T>, T> collector) {
   return Collectors.collectingAndThen(Collectors.toList(), collected -> collected.get(0));
 }
 

If suppressions become too wide spread and annoying it might be reasonable to update Check with option to ignore wildcard if used with another type (not alone).

Since:

1.9.0

Author:

Baratali Izmailov

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 and Description
static String	MSG_KEY Key for error message.

Constructor Summary

Constructors

Constructor and Description
ForbidWildcardAsReturnTypeCheck()

Method Summary

Modifier and Type	Method and Description
int[]	getAcceptableTokens()
int[]	getDefaultTokens()
int[]	getRequiredTokens()
void	setAllowReturnWildcardWithExtends(boolean allowReturnWildcardWithExtends) Setter for allowReturnWildcardWithExtends.
void	setAllowReturnWildcardWithSuper(boolean allowReturnWildcardWithSuper) Setter for allowReturnWildcardWithSuper.
void	setCheckDeprecatedMethods(boolean checkDeprecatedMethods) Setter for checkDeprecatedMethods.
void	setCheckOverrideMethods(boolean checkOverrideMethods) Setter for checkOverrideMethods.
void	setCheckPackageMethods(boolean checkPackageMethods) Setter for checkPackageMethods.
void	setCheckPrivateMethods(boolean checkPrivateMethods) Setter for checkPrivateMethods.
void	setCheckProtectedMethods(boolean checkProtectedMethods) Setter for checkProtectedMethods.
void	setCheckPublicMethods(boolean checkPublicMethods) Setter for checkPublicMethods.
void	setReturnTypeClassNamesIgnoreRegex(String returnTypeClassNamesIgnoreRegex) Setter for returnTypeClassNamesIgnoreRegex.
void	visitToken(com.puppycrawl.tools.checkstyle.api.DetailAST methodDefAst)

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

beginTree, clearMessages, destroy, finishTree, getFileContents, getLine, getLines, getMessages, getTabWidth, getTokenNames, 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

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 String MSG_KEY

Key for error message.

See Also:

Constant Field Values

Constructor Detail

ForbidWildcardAsReturnTypeCheck

public ForbidWildcardAsReturnTypeCheck()

Method Detail

setCheckPublicMethods

public void setCheckPublicMethods(boolean checkPublicMethods)

Setter for checkPublicMethods.

Parameters:

checkPublicMethods - New value for the field.

setCheckProtectedMethods

public void setCheckProtectedMethods(boolean checkProtectedMethods)

Setter for checkProtectedMethods.

Parameters:

checkProtectedMethods - New value for the field.

setCheckPackageMethods

public void setCheckPackageMethods(boolean checkPackageMethods)

Setter for checkPackageMethods.

Parameters:

checkPackageMethods - New value for the field.

setCheckPrivateMethods

public void setCheckPrivateMethods(boolean checkPrivateMethods)

Setter for checkPrivateMethods.

Parameters:

checkPrivateMethods - New value for the field.

setCheckOverrideMethods

public void setCheckOverrideMethods(boolean checkOverrideMethods)

Setter for checkOverrideMethods.

Parameters:

checkOverrideMethods - New value for the field.

setCheckDeprecatedMethods

public void setCheckDeprecatedMethods(boolean checkDeprecatedMethods)

Setter for checkDeprecatedMethods.

Parameters:

checkDeprecatedMethods - New value for the field.

setAllowReturnWildcardWithSuper

public void setAllowReturnWildcardWithSuper(boolean allowReturnWildcardWithSuper)

Setter for allowReturnWildcardWithSuper.

Parameters:

allowReturnWildcardWithSuper - New value for the field.

setAllowReturnWildcardWithExtends

public void setAllowReturnWildcardWithExtends(boolean allowReturnWildcardWithExtends)

Setter for allowReturnWildcardWithExtends.

Parameters:

allowReturnWildcardWithExtends - New value for the field.

setReturnTypeClassNamesIgnoreRegex

public void setReturnTypeClassNamesIgnoreRegex(String returnTypeClassNamesIgnoreRegex)

Setter for returnTypeClassNamesIgnoreRegex.

Parameters:

returnTypeClassNamesIgnoreRegex - New value for the field.

getDefaultTokens

public int[] getDefaultTokens()

Specified by:

getDefaultTokens in class com.puppycrawl.tools.checkstyle.api.AbstractCheck

getAcceptableTokens

public int[] getAcceptableTokens()

Specified by:

getAcceptableTokens in class com.puppycrawl.tools.checkstyle.api.AbstractCheck

getRequiredTokens

public int[] getRequiredTokens()

Specified by:

getRequiredTokens in class com.puppycrawl.tools.checkstyle.api.AbstractCheck

visitToken

public void visitToken(com.puppycrawl.tools.checkstyle.api.DetailAST methodDefAst)

Overrides:

visitToken in class com.puppycrawl.tools.checkstyle.api.AbstractCheck