Class UnusedImportsCheck
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.imports.UnusedImportsCheck
- All Implemented Interfaces:
Configurable
,Contextualizable
Checks for unused import statements. Checkstyle uses a simple but very reliable algorithm to report on 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. - It is a duplicate of another import. This is when a class is imported more than once.
-
The class imported is from the
java.lang
package. For example importingjava.lang.String
. - The class imported is from the same package.
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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.List
would be considered referenced with the Javadoc comment{@link List}
. The alternative to avoid introducing a compile time dependency would be to write the Javadoc comment as{@link java.util.List}
.
The main limitation of this check is handling the case where an imported type has the same name as a declaration, such as a member variable.
For example, in the following case the import java.awt.Component
will not be flagged as unused:
import java.awt.Component; class FooBar { private Object Component; // a bad practice in my opinion ... }
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Property
processJavadoc
- Control whether to process Javadoc comments. Type isboolean
. Default value istrue
.
To configure the check:
<module name="UnusedImports"/>
Parent is com.puppycrawl.tools.checkstyle.TreeWalker
Violation Message Keys:
-
import.unused
- Since:
- 3.0
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Nested Class Summary
Nested classes/interfaces inherited from class com.puppycrawl.tools.checkstyle.api.AutomaticBean
AutomaticBean.OutputStreamOptions
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Field Summary
Fields -
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionvoid
Called before the starting to process a tree.void
finishTree
(DetailAST rootAST) Called after finished processing a tree.int[]
The configurable token set.int[]
Returns the default token a check is interested in.int[]
The tokens that this check must be registered for.void
setProcessJavadoc
(boolean value) Setter to control whether to process Javadoc comments.void
visitToken
(DetailAST ast) Called to process a token.Methods inherited from class com.puppycrawl.tools.checkstyle.api.AbstractCheck
clearMessages, destroy, 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
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Field Details
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MSG_KEY
A key is pointing to the warning message text in "messages.properties" file.- See Also:
-
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Constructor Details
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UnusedImportsCheck
public UnusedImportsCheck()
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Method Details
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setProcessJavadoc
public void setProcessJavadoc(boolean value) Setter to control whether to process Javadoc comments.- Parameters:
value
- Flag for processing Javadoc comments.
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beginTree
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 classAbstractCheck
- Parameters:
rootAST
- the root of the tree
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finishTree
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 classAbstractCheck
- Parameters:
rootAST
- the root of the tree
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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 classAbstractCheck
- Returns:
- the default tokens
- See Also:
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getRequiredTokens
public int[] getRequiredTokens()Description copied from class:AbstractCheck
The tokens that this check must be registered for.- Specified by:
getRequiredTokens
in classAbstractCheck
- Returns:
- the token set this must be registered for.
- See Also:
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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 classAbstractCheck
- Returns:
- the token set this check is designed for.
- See Also:
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visitToken
Description copied from class:AbstractCheck
Called to process a token.- Overrides:
visitToken
in classAbstractCheck
- Parameters:
ast
- the token to process
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