Class UnusedLocalVariableCheck
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.coding.UnusedLocalVariableCheck
- All Implemented Interfaces:
Configurable
,Contextualizable
Checks that a local variable is declared and/or assigned, but not used. Doesn't support pattern variables yet. Doesn't check array components as array components are classified as different kind of variables by JLS.
To configure the check:
<module name="UnusedLocalVariable"/>
Example:
class Test { int a; { int k = 12; // violation, assigned and updated but never used k++; } Test(int a) { // ok as 'a' is a constructor parameter not a local variable this.a = 12; } void method(int b) { int a = 10; // violation int[] arr = {1, 2, 3}; // violation int[] anotherArr = {1}; // ok anotherArr[0] = 4; } String convertValue(String newValue) { String s = newValue.toLowerCase(); // violation return newValue.toLowerCase(); } void read() throws IOException { BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); String s; // violation while ((s = reader.readLine()) != null) { } try (BufferedReader reader1 // ok as 'reader1' is a resource and resources are closed // at the end of the statement = new BufferedReader(new FileReader("abc.txt"))) { } try { } catch (Exception e) { // ok as e is an exception parameter } } void loops() { int j = 12; for (int i = 0; j < 11; i++) { // violation, unused local variable 'i'. } for (int p = 0; j < 11; p++) // ok p /= 2; } void lambdas() { Predicate<String> obj = (String str) -> { // ok as 'str' is a lambda parameter return true; }; obj.test("test"); } }
Parent is com.puppycrawl.tools.checkstyle.TreeWalker
Violation Message Keys:
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unused.local.var
- Since:
- 9.3
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Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionprivate static class
Maintains information about the type declaration.private static final class
Maintains information about the variable.Nested classes/interfaces inherited from class com.puppycrawl.tools.checkstyle.api.AutomaticBean
AutomaticBean.OutputStreamOptions
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Field Summary
FieldsModifier and TypeFieldDescriptionprivate final Map
<DetailAST, UnusedLocalVariableCheck.TypeDeclDesc> Maps local anonymous inner class to the TypeDeclDesc object containing it.Set of tokens of typeCONTAINERS_FOR_ANON_INNERS
andTokenTypes.LAMBDA
in some cases.private static final int[]
An array of blocks in which local anon inner classes can exist.private int
Depth at which a type declaration is nested, 0 for top level type declarations.private static final int[]
An array of increment and decrement tokens.static final String
A key is pointing to the warning message text in "messages.properties" file.private static final String
Package separator.private String
Name of the package.private static final int[]
An array of scope tokens.private final Deque
<UnusedLocalVariableCheck.TypeDeclDesc> Keeps track of all the type declarations present in the file.private final Map
<DetailAST, UnusedLocalVariableCheck.TypeDeclDesc> Maps type declaration ast to their respective TypeDeclDesc objects.private static final int[]
An array of unacceptable children of ast of typeTokenTypes.DOT
.private static final int[]
An array of unacceptable parent of ast of typeTokenTypes.IDENT
.private final Deque
<UnusedLocalVariableCheck.VariableDesc> Keeps tracks of the variables declared in file. -
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionprivate void
addInstanceOrClassVar
(DetailAST varDefAst) Add instance variables and class variables to theUnusedLocalVariableCheck.TypeDeclDesc.instanceAndClassVarStack
.private static void
addLocalVariables
(DetailAST varDefAst, Deque<UnusedLocalVariableCheck.VariableDesc> variablesStack) Add local variables to thevariablesStack
stack.void
Called before the starting to process a tree.private static void
checkIdentifierAst
(DetailAST identAst, Deque<UnusedLocalVariableCheck.VariableDesc> variablesStack) Checks the identifier ast.private void
customLeaveToken
(DetailAST ast, Deque<UnusedLocalVariableCheck.VariableDesc> variablesStack) Leave all ast nodes underanonInnerClassHolders
once again.private void
customVisitToken
(DetailAST ast, Deque<UnusedLocalVariableCheck.VariableDesc> variablesStack) Visit all ast nodes underanonInnerClassHolders
once again.private static String
Get name of package and super class of anon inner class by concatenating the identifier values underTokenTypes.DOT
.private static DetailAST
findScopeOfVariable
(DetailAST variableDef) Find the scope of variable.int[]
The configurable token set.private static DetailAST
getBlockContainingLocalAnonInnerClass
(DetailAST literalNewAst) Get the block containing local anon inner class.int[]
Returns the default token a check is interested in.private String
getQualifiedTypeDeclarationName
(DetailAST typeDeclAst) Get qualified type declaration name from type ast.private static String
getQualifiedTypeDeclarationName
(String packageName, String outerClassQualifiedName, String className) Get the qualified name of type declaration by combiningpackageName
,outerClassQualifiedName
andclassName
.int[]
The tokens that this check must be registered for.static String
getShortNameOfAnonInnerClass
(DetailAST literalNewAst) Get the short name of super class of anonymous inner class.getSuperClassOfAnonInnerClass
(DetailAST literalNewAst) Get theUnusedLocalVariableCheck.TypeDeclDesc
of the super class of anonymous inner class.private static UnusedLocalVariableCheck.TypeDeclDesc
getTheNearestClass
(String outerTypeDeclName, List<UnusedLocalVariableCheck.TypeDeclDesc> typeDeclWithSameName) For all type declarations with the same name as the superclass, gets the nearest type declaration.private boolean
hasSameNameAsSuperClass
(String superClassName, UnusedLocalVariableCheck.TypeDeclDesc typeDeclDesc) Whether the qualified name oftypeDeclDesc
matches the super class name.private static boolean
A variable with increment or decrement operator is considered used if it is used as an argument or as an array index or for assigning value to a variable.private static boolean
isInsideLocalAnonInnerClass
(DetailAST literalNewAst) Whether ast node of typeTokenTypes.LITERAL_NEW
is a part of a local anonymous inner class.private static boolean
isLeftHandSideValue
(DetailAST identAst) Checks whether the ast of typeTokenTypes.IDENT
is used as left-hand side value.private static boolean
isNonLocalTypeDeclaration
(DetailAST typeDeclAst) Whether a type declaration is non-local.private static boolean
isPrivateInstanceVariable
(DetailAST varDefAst) Whether instance variable or class variable have private access modifier.private static boolean
isStandAloneIncrementOrDecrement
(DetailAST identAst) Checks whether the ast of typeTokenTypes.IDENT
is used as an operand of a stand-alone increment or decrement.private void
iterateOverBlockContainingLocalAnonInnerClass
(DetailAST ast, Deque<UnusedLocalVariableCheck.VariableDesc> variablesStack) Iterate over all the ast nodes present underast
.private void
We process all the blocks containing local anonymous inner classes separately after processing all the other nodes.void
leaveToken
(DetailAST ast) Called after all the child nodes have been process.private void
logViolations
(DetailAST scopeAst, Deque<UnusedLocalVariableCheck.VariableDesc> variablesStack) TraversevariablesStack
stack and log the violations.private void
modifyVariablesStack
(UnusedLocalVariableCheck.TypeDeclDesc obtainedClass, Deque<UnusedLocalVariableCheck.VariableDesc> variablesStack, DetailAST literalNewAst) Add non-private instance and class variables of the super class of the anonymous class to the variables stack.static boolean
Whether to check identifier token nested under dotAst.static boolean
shouldCheckIdentWithMethodRefParent
(DetailAST identAst) Whether an ident with parent node of typeTokenTypes.METHOD_REF
should be checked or not.private static int
typeDeclNameMatchingCount
(String patternClass, String classToBeMatched) Calculates and returns the type declaration name matching count.typeDeclWithSameName
(String superClassName) Checks if there is a type declaration with same name as the super class.private static void
visitDotToken
(DetailAST dotAst, Deque<UnusedLocalVariableCheck.VariableDesc> variablesStack) Visit ast of typeTokenTypes.DOT
.private static void
visitIdentToken
(DetailAST identAst, Deque<UnusedLocalVariableCheck.VariableDesc> variablesStack) Visit ast of typeTokenTypes.IDENT
.private void
visitLocalAnonInnerClass
(DetailAST literalNewAst) Visit the local anon inner class.void
visitToken
(DetailAST ast) Called to process a token.private void
visitTypeDeclarationToken
(DetailAST typeDeclAst) Visit the type declaration token.private void
visitVariableDefToken
(DetailAST varDefAst) Visit ast of typeTokenTypes.VARIABLE_DEF
.Methods inherited from class com.puppycrawl.tools.checkstyle.api.AbstractCheck
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
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Field Details
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MSG_UNUSED_LOCAL_VARIABLE
A key is pointing to the warning message text in "messages.properties" file.- See Also:
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INCREMENT_AND_DECREMENT_TOKENS
private static final int[] INCREMENT_AND_DECREMENT_TOKENSAn array of increment and decrement tokens. -
SCOPES
private static final int[] SCOPESAn array of scope tokens. -
UNACCEPTABLE_CHILD_OF_DOT
private static final int[] UNACCEPTABLE_CHILD_OF_DOTAn array of unacceptable children of ast of typeTokenTypes.DOT
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UNACCEPTABLE_PARENT_OF_IDENT
private static final int[] UNACCEPTABLE_PARENT_OF_IDENTAn array of unacceptable parent of ast of typeTokenTypes.IDENT
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CONTAINERS_FOR_ANON_INNERS
private static final int[] CONTAINERS_FOR_ANON_INNERSAn array of blocks in which local anon inner classes can exist. -
PACKAGE_SEPARATOR
Package separator.- See Also:
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variables
Keeps tracks of the variables declared in file. -
typeDeclarations
Keeps track of all the type declarations present in the file. Pops the type out of the stack while leaving the type in visitor pattern. -
typeDeclAstToTypeDeclDesc
Maps type declaration ast to their respective TypeDeclDesc objects. -
anonInnerAstToTypeDeclDesc
Maps local anonymous inner class to the TypeDeclDesc object containing it. -
anonInnerClassHolders
Set of tokens of typeCONTAINERS_FOR_ANON_INNERS
andTokenTypes.LAMBDA
in some cases. -
packageName
Name of the package. -
depth
private int depthDepth at which a type declaration is nested, 0 for top level type declarations.
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Constructor Details
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UnusedLocalVariableCheck
public UnusedLocalVariableCheck()Creates a newUnusedLocalVariableCheck
instance.
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Method Details
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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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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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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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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:
root
- the root of the tree
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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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leaveToken
Description copied from class:AbstractCheck
Called after all the child nodes have been process.- Overrides:
leaveToken
in classAbstractCheck
- Parameters:
ast
- the token leaving
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visitDotToken
private static void visitDotToken(DetailAST dotAst, Deque<UnusedLocalVariableCheck.VariableDesc> variablesStack) Visit ast of typeTokenTypes.DOT
.- Parameters:
dotAst
- dotAstvariablesStack
- stack of all the relevant variables in the scope
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visitVariableDefToken
Visit ast of typeTokenTypes.VARIABLE_DEF
.- Parameters:
varDefAst
- varDefAst
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visitIdentToken
private static void visitIdentToken(DetailAST identAst, Deque<UnusedLocalVariableCheck.VariableDesc> variablesStack) Visit ast of typeTokenTypes.IDENT
.- Parameters:
identAst
- identAstvariablesStack
- stack of all the relevant variables in the scope
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visitTypeDeclarationToken
Visit the type declaration token.- Parameters:
typeDeclAst
- type declaration ast
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visitLocalAnonInnerClass
Visit the local anon inner class.- Parameters:
literalNewAst
- literalNewAst
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extractQualifiedName
Get name of package and super class of anon inner class by concatenating the identifier values underTokenTypes.DOT
. Duplicated, until https://github.com/checkstyle/checkstyle/issues/11201- Parameters:
ast
- ast to extract superclass or package name from- Returns:
- qualified name
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isInsideLocalAnonInnerClass
Whether ast node of typeTokenTypes.LITERAL_NEW
is a part of a local anonymous inner class.- Parameters:
literalNewAst
- ast node of typeTokenTypes.LITERAL_NEW
- Returns:
- true if variableDefAst is an instance variable in local anonymous inner class
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logViolations
private void logViolations(DetailAST scopeAst, Deque<UnusedLocalVariableCheck.VariableDesc> variablesStack) TraversevariablesStack
stack and log the violations.- Parameters:
scopeAst
- ast node of typeSCOPES
variablesStack
- stack of all the relevant variables in the scope
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leaveCompilationUnit
private void leaveCompilationUnit()We process all the blocks containing local anonymous inner classes separately after processing all the other nodes. This is being done due to the fact the instance variables of local anon inner classes can cast a shadow on local variables. -
isNonLocalTypeDeclaration
Whether a type declaration is non-local. Annotated interfaces are always non-local.- Parameters:
typeDeclAst
- type declaration ast- Returns:
- true if type declaration is non-local
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getBlockContainingLocalAnonInnerClass
Get the block containing local anon inner class.- Parameters:
literalNewAst
- ast node of typeTokenTypes.LITERAL_NEW
- Returns:
- the block containing local anon inner class
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addLocalVariables
private static void addLocalVariables(DetailAST varDefAst, Deque<UnusedLocalVariableCheck.VariableDesc> variablesStack) Add local variables to thevariablesStack
stack. Also adds the instance variables defined in a local anonymous inner class.- Parameters:
varDefAst
- ast node of typeTokenTypes.VARIABLE_DEF
variablesStack
- stack of all the relevant variables in the scope
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addInstanceOrClassVar
Add instance variables and class variables to theUnusedLocalVariableCheck.TypeDeclDesc.instanceAndClassVarStack
.- Parameters:
varDefAst
- ast node of typeTokenTypes.VARIABLE_DEF
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isPrivateInstanceVariable
Whether instance variable or class variable have private access modifier.- Parameters:
varDefAst
- ast node of typeTokenTypes.VARIABLE_DEF
- Returns:
- true if instance variable or class variable have private access modifier
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getSuperClassOfAnonInnerClass
private UnusedLocalVariableCheck.TypeDeclDesc getSuperClassOfAnonInnerClass(DetailAST literalNewAst) Get theUnusedLocalVariableCheck.TypeDeclDesc
of the super class of anonymous inner class.- Parameters:
literalNewAst
- ast node of typeTokenTypes.LITERAL_NEW
- Returns:
UnusedLocalVariableCheck.TypeDeclDesc
of the super class of anonymous inner class
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getShortNameOfAnonInnerClass
Get the short name of super class of anonymous inner class. Example-TestClass.NestedClass obj = new Test().new NestedClass() {}; // Short name will be Test.NestedClass
- Parameters:
literalNewAst
- ast node of typeTokenTypes.LITERAL_NEW
- Returns:
- short name of base class of anonymous inner class
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modifyVariablesStack
private void modifyVariablesStack(UnusedLocalVariableCheck.TypeDeclDesc obtainedClass, Deque<UnusedLocalVariableCheck.VariableDesc> variablesStack, DetailAST literalNewAst) Add non-private instance and class variables of the super class of the anonymous class to the variables stack.- Parameters:
obtainedClass
- super class of the anon inner classvariablesStack
- stack of all the relevant variables in the scopeliteralNewAst
- ast node of typeTokenTypes.LITERAL_NEW
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typeDeclWithSameName
Checks if there is a type declaration with same name as the super class. Duplicated, until https://github.com/checkstyle/checkstyle/issues/11201- Parameters:
superClassName
- name of the super class- Returns:
- true if there is another type declaration with same name.
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hasSameNameAsSuperClass
private boolean hasSameNameAsSuperClass(String superClassName, UnusedLocalVariableCheck.TypeDeclDesc typeDeclDesc) Whether the qualified name oftypeDeclDesc
matches the super class name.- Parameters:
superClassName
- name of the super classtypeDeclDesc
- type declaration description- Returns:
true
if the qualified name oftypeDeclDesc
matches the super class name
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getTheNearestClass
private static UnusedLocalVariableCheck.TypeDeclDesc getTheNearestClass(String outerTypeDeclName, List<UnusedLocalVariableCheck.TypeDeclDesc> typeDeclWithSameName) For all type declarations with the same name as the superclass, gets the nearest type declaration. Duplicated, until https://github.com/checkstyle/checkstyle/issues/11201- Parameters:
outerTypeDeclName
- outer type declaration of anonymous inner classtypeDeclWithSameName
- typeDeclarations which have the same name as the super class- Returns:
- the nearest class
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typeDeclNameMatchingCount
Calculates and returns the type declaration name matching count.Suppose our pattern class is
Duplicated, until https://github.com/checkstyle/checkstyle/issues/11201foo.a.b
and class to be matched isfoo.a.ball
then type declaration name matching count would be calculated by comparing every character, and updating main counter when we hit "." to prevent matching "a.b" with "a.ball". In this case type declaration name matching count would be equal to 6 and not 7 (b of ball is not counted).- Parameters:
patternClass
- class against which the given class has to be matchedclassToBeMatched
- class to be matched- Returns:
- class name matching count
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getQualifiedTypeDeclarationName
Get qualified type declaration name from type ast. Duplicated, until https://github.com/checkstyle/checkstyle/issues/11201- Parameters:
typeDeclAst
- type declaration ast- Returns:
- qualified name of type declaration
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getQualifiedTypeDeclarationName
private static String getQualifiedTypeDeclarationName(String packageName, String outerClassQualifiedName, String className) Get the qualified name of type declaration by combiningpackageName
,outerClassQualifiedName
andclassName
. Duplicated, until https://github.com/checkstyle/checkstyle/issues/11201- Parameters:
packageName
- packageNameouterClassQualifiedName
- outerClassQualifiedNameclassName
- className- Returns:
- the qualified name of type declaration by combining
packageName
,outerClassQualifiedName
andclassName
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iterateOverBlockContainingLocalAnonInnerClass
private void iterateOverBlockContainingLocalAnonInnerClass(DetailAST ast, Deque<UnusedLocalVariableCheck.VariableDesc> variablesStack) Iterate over all the ast nodes present underast
.- Parameters:
ast
- astvariablesStack
- stack of all the relevant variables in the scope
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customVisitToken
private void customVisitToken(DetailAST ast, Deque<UnusedLocalVariableCheck.VariableDesc> variablesStack) Visit all ast nodes underanonInnerClassHolders
once again.- Parameters:
ast
- astvariablesStack
- stack of all the relevant variables in the scope
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customLeaveToken
private void customLeaveToken(DetailAST ast, Deque<UnusedLocalVariableCheck.VariableDesc> variablesStack) Leave all ast nodes underanonInnerClassHolders
once again.- Parameters:
ast
- astvariablesStack
- stack of all the relevant variables in the scope
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shouldCheckIdentWithMethodRefParent
Whether an ident with parent node of typeTokenTypes.METHOD_REF
should be checked or not.- Parameters:
identAst
- identAst- Returns:
- true if an ident with parent node of type
TokenTypes.METHOD_REF
should be checked or if the parent type is notTokenTypes.METHOD_REF
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shouldCheckIdentTokenNestedUnderDot
Whether to check identifier token nested under dotAst.- Parameters:
dotAst
- dotAst- Returns:
- true if ident nested under dotAst should be checked
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checkIdentifierAst
private static void checkIdentifierAst(DetailAST identAst, Deque<UnusedLocalVariableCheck.VariableDesc> variablesStack) Checks the identifier ast.- Parameters:
identAst
- ast of typeTokenTypes.IDENT
variablesStack
- stack of all the relevant variables in the scope
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findScopeOfVariable
Find the scope of variable.- Parameters:
variableDef
- ast of typeTokenTypes.VARIABLE_DEF
- Returns:
- scope of variableDef
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isLeftHandSideValue
Checks whether the ast of typeTokenTypes.IDENT
is used as left-hand side value. An identifier is being used as a left-hand side value if it is used as the left operand of an assignment or as an operand of a stand-alone increment or decrement.- Parameters:
identAst
- ast of typeTokenTypes.IDENT
- Returns:
- true if identAst is used as a left-hand side value
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isStandAloneIncrementOrDecrement
Checks whether the ast of typeTokenTypes.IDENT
is used as an operand of a stand-alone increment or decrement.- Parameters:
identAst
- ast of typeTokenTypes.IDENT
- Returns:
- true if identAst is used as an operand of stand-alone increment or decrement
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isIncrementOrDecrementVariableUsed
A variable with increment or decrement operator is considered used if it is used as an argument or as an array index or for assigning value to a variable.- Parameters:
exprAst
- ast of typeTokenTypes.EXPR
- Returns:
- true if variable nested in exprAst is used
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