Package com.puppycrawl.tools.checkstyle.checks.imports

Class UnusedImportsCheck

java.lang.Object

com.puppycrawl.tools.checkstyle.AbstractAutomaticBean

com.puppycrawl.tools.checkstyle.api.AbstractViolationReporter

com.puppycrawl.tools.checkstyle.api.AbstractCheck

com.puppycrawl.tools.checkstyle.checks.javadoc.AbstractJavadocCheck

com.puppycrawl.tools.checkstyle.checks.imports.UnusedImportsCheck

All Implemented Interfaces:

Configurable, Contextualizable

public class UnusedImportsCheck
extends AbstractJavadocCheck

Checks for unused import statements. An import statement is considered unused if:

• It is not referenced in the file. The algorithm does not support wild-card imports like import java.io.*;. Most IDE's provide very sophisticated checks for imports that handle wild-card imports.
• The class imported is from the java.lang package. For example importing java.lang.String.
• The class imported is from the same package.
• A static method is imported when used as method reference. In that case, only the type needs to be imported and that's enough to resolve the method.
• Optionally: it is referenced in Javadoc comments. This check is on by default, but it is considered bad practice to introduce a compile-time dependency for documentation purposes only. As an example, the import java.util.Set would be considered referenced with the Javadoc comment {@link Set}. The alternative to avoid introducing a compile-time dependency would be to write the Javadoc comment as {@link Set}.

The main limitation of this check is handling the cases where:

• An imported type has the same name as a declaration, such as a member variable.
• There are two or more static imports with the same method name (javac can distinguish imports with same name but different parameters, but checkstyle can not due to limitation.)
• Module import declarations are used. Checkstyle does not resolve modules and therefore cannot determine which packages or types are brought into scope by an import module declaration. See limitations.

Since:

3.0

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private static final class	UnusedImportsCheck.Frame	Holds the names of referenced types and names of declared inner types.

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

AbstractAutomaticBean.OutputStreamOptions

Field Summary

Fields

Modifier and Type	Field	Description
private UnusedImportsCheck.Frame	currentFrame	The scope is being processed.
private final Set<FullIdent>	imports	Set of the imports.
private static final Pattern	JAVA_LANG_PACKAGE_PATTERN	Regexp pattern to match java.lang package.
static final String	MSG_KEY	A key is pointing to the warning message text in "messages.properties" file.
private boolean	processJavadoc	Control whether to process Javadoc comments.
private static final String	STAR_IMPORT_SUFFIX	Suffix for the star import.

Fields inherited from class com.puppycrawl.tools.checkstyle.checks.javadoc.AbstractJavadocCheck

MSG_JAVADOC_PARSE_RULE_ERROR, MSG_KEY_UNCLOSED_HTML_TAG

Constructor Summary

Constructors

Constructor	Description
UnusedImportsCheck()

Method Summary

Modifier and Type	Method	Description
void	beginTree(DetailAST rootAST)	Called before the starting to process a tree.
void	finishTree(DetailAST rootAST)	Called after finished processing a tree.
int[]	getAcceptableTokens()	The configurable token set.
int[]	getDefaultJavadocTokens()	Returns the default javadoc token types a check is interested in.
int[]	getDefaultTokens()	Returns the default token a check is interested in.
int[]	getRequiredJavadocTokens()	The javadoc tokens that this check must be registered for.
int[]	getRequiredTokens()	The tokens that this check must be registered for.
private static boolean	isQualifiedIdentifier(DetailAST ast)	Checks whether ast is a fully qualified identifier.
private boolean	isUnusedImport(String imprt)	Checks whether an import is unused.
void	leaveToken(DetailAST ast)	Called after all the child nodes have been process.
private void	processException(DetailNode ast)	Processes a Javadoc throws or exception tag to record referenced type.
private void	processIdent(DetailAST ast)	Collects references made by IDENT.
private void	processImport(DetailAST ast)	Collects the details of imports.
private void	processParameterType(DetailNode ast)	Processes a Javadoc parameter type tag to record referenced type.
private void	processReference(DetailNode ast)	Processes a Javadoc reference to record referenced types.
private void	processStaticImport(DetailAST ast)	Collects the details of static imports.
void	setProcessJavadoc(boolean value)	Setter to control whether to process Javadoc comments.
void	setViolateExecutionOnNonTightHtml(boolean shouldReportViolation)	Setter to control when to print violations if the Javadoc being examined by this check violates the tight html rules defined at Tight-HTML Rules.
private static String	topLevelType(String type)	If the given type string contains "."
void	visitJavadocToken(DetailNode ast)	Called to process a Javadoc token.
void	visitToken(DetailAST ast)	Called to process a token.

Methods inherited from class com.puppycrawl.tools.checkstyle.checks.javadoc.AbstractJavadocCheck

acceptJavadocWithNonTightHtml, beginJavadocTree, destroy, finishJavadocTree, getAcceptableJavadocTokens, getBlockCommentAst, init, isCommentNodesRequired, leaveJavadocToken, setJavadocTokens

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

clearViolations, getFileContents, getFilePath, getLine, getLineCodePoints, getLines, getTabWidth, getTokenNames, getViolations, 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.AbstractAutomaticBean

configure, contextualize, getConfiguration, setupChild

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

MSG_KEY

public static final String MSG_KEY

A key is pointing to the warning message text in "messages.properties" file.

See Also:

• Constant Field Values

JAVA_LANG_PACKAGE_PATTERN

private static final Pattern JAVA_LANG_PACKAGE_PATTERN

Regexp pattern to match java.lang package.

STAR_IMPORT_SUFFIX

private static final String STAR_IMPORT_SUFFIX

Suffix for the star import.

See Also:

• Constant Field Values

imports

private final Set<FullIdent> imports

Set of the imports.

processJavadoc

private boolean processJavadoc

Control whether to process Javadoc comments.

currentFrame

private UnusedImportsCheck.Frame currentFrame

The scope is being processed. Types declared in a scope can shadow imported types.

Constructor Details

UnusedImportsCheck

public UnusedImportsCheck()

Method Details

setProcessJavadoc

public void setProcessJavadoc(boolean value)

Setter to control whether to process Javadoc comments.

Parameters:

value - Flag for processing Javadoc comments.

Since:

5.4

setViolateExecutionOnNonTightHtml

public void setViolateExecutionOnNonTightHtml(boolean shouldReportViolation)

Setter to control when to print violations if the Javadoc being examined by this check violates the tight html rules defined at Tight-HTML Rules.

Overrides:

setViolateExecutionOnNonTightHtml in class AbstractJavadocCheck

Parameters:

shouldReportViolation - value to which the field shall be set to

Since:

8.3

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 AbstractJavadocCheck

Parameters:

rootAST - the root of the tree

finishTree

public void finishTree(DetailAST rootAST)

Description copied from class: AbstractCheck

Called after finished processing a tree. Ideal place to report on information collected whilst processing a tree.

Overrides:

finishTree in class AbstractCheck

Parameters:

rootAST - the root of the tree

getRequiredJavadocTokens

public int[] getRequiredJavadocTokens()

Description copied from class: AbstractJavadocCheck

The javadoc tokens that this check must be registered for.

Overrides:

getRequiredJavadocTokens in class AbstractJavadocCheck

Returns:

the javadoc token set this must be registered for.

See Also:

• JavadocCommentsTokenTypes

getDefaultJavadocTokens

public int[] getDefaultJavadocTokens()

Description copied from class: AbstractJavadocCheck

Returns the default javadoc token types a check is interested in.

Specified by:

getDefaultJavadocTokens in class AbstractJavadocCheck

Returns:

the default javadoc token types

See Also:

• JavadocCommentsTokenTypes

visitJavadocToken

public void visitJavadocToken(DetailNode ast)

Description copied from class: AbstractJavadocCheck

Called to process a Javadoc token.

Specified by:

visitJavadocToken in class AbstractJavadocCheck

Parameters:

ast - the token to process

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.

Overrides:

getDefaultTokens in class AbstractJavadocCheck

Returns:

the default tokens

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.

Overrides:

getAcceptableTokens in class AbstractJavadocCheck

Returns:

the token set this check is designed for.

See Also:

• TokenTypes

getRequiredTokens

public int[] getRequiredTokens()

Description copied from class: AbstractCheck

The tokens that this check must be registered for.

Overrides:

getRequiredTokens in class AbstractJavadocCheck

Returns:

the token set this must be registered for.

See Also:

• TokenTypes

visitToken

public void visitToken(DetailAST ast)

Description copied from class: AbstractCheck

Called to process a token.

Overrides:

visitToken in class AbstractJavadocCheck

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

isUnusedImport

private boolean isUnusedImport(String imprt)

Checks whether an import is unused.

Parameters:

imprt - an import.

Returns:

true if an import is unused.

processIdent

private void processIdent(DetailAST ast)

Collects references made by IDENT.

Parameters:

ast - the IDENT node to process

isQualifiedIdentifier

private static boolean isQualifiedIdentifier(DetailAST ast)

Checks whether ast is a fully qualified identifier.

Parameters:

ast - to check

Returns:

true if given ast is a fully qualified identifier

processImport

private void processImport(DetailAST ast)

Collects the details of imports.

Parameters:

ast - node containing the import details

processStaticImport

private void processStaticImport(DetailAST ast)

Collects the details of static imports.

Parameters:

ast - node containing the static import details

processReference

private void processReference(DetailNode ast)

Processes a Javadoc reference to record referenced types.

Parameters:

ast - the Javadoc reference node

processParameterType

private void processParameterType(DetailNode ast)

Processes a Javadoc parameter type tag to record referenced type.

Parameters:

ast - the Javadoc parameter type node

processException

private void processException(DetailNode ast)

Processes a Javadoc throws or exception tag to record referenced type.

Parameters:

ast - the Javadoc throws or exception node

topLevelType

private static String topLevelType(String type)

If the given type string contains "." (e.g. "Map.Entry"), returns the top level type (e.g. "Map"), as that is what must be imported for the type to resolve. Otherwise, returns the type as-is.

Parameters:

type - A possibly qualified type name

Returns:

The simple name of the top level type