Class EqualsHashCodeCheck
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.EqualsHashCodeCheck
- All Implemented Interfaces:
Configurable
,Contextualizable
Checks that classes that either override equals()
or hashCode()
also
overrides the other.
This check only verifies that the method declarations match Object.equals(Object)
and
Object.hashCode()
exactly to be considered an override. This check does not verify
invalid method names, parameters other than Object
, or anything else.
Rationale: The contract of equals()
and hashCode()
requires that
equal objects have the same hashCode. Therefore, whenever you override
equals()
you must override hashCode()
to ensure that your class can
be used in hash-based collections.
To configure the check:
<module name="EqualsHashCode"/>
Example:
public static class Example1 { public int hashCode() { // code } public boolean equals(String o) { // violation, overloaded implementation of 'equals' // code } } public static class Example2 { public boolean equals(Object o) { // violation, no 'hashCode' // code } public boolean equals(String o) { // code } } public static class Example3 { public int hashCode() { // code } public boolean equals(Object o) { // OK // code } public boolean equals(String o) { // code } } public static class Example4 { public int hashCode() { // code } public boolean equals(java.lang.Object o) { // OK // code } } public static class Example5 { public static int hashCode(int i) { // code } public boolean equals(Object o) { // violation, overloaded implementation of 'hashCode' // code } } public static class Example6 { public int hashCode() { // violation, overloaded implementation of 'equals' // code } public static boolean equals(Object o, Object o2) { // code } }
Parent is com.puppycrawl.tools.checkstyle.TreeWalker
Violation Message Keys:
-
equals.noEquals
-
equals.noHashCode
- Since:
- 3.0
-
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
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_HASHCODE
A key is pointing to the warning message text in "messages.properties" file.- See Also:
-
MSG_KEY_EQUALS
A key is pointing to the warning message text in "messages.properties" file.- See Also:
-
-
Constructor Details
-
EqualsHashCodeCheck
public EqualsHashCodeCheck()
-
-
Method Details
-
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:
-
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:
-
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:
-
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
-
visitToken
Description copied from class:AbstractCheck
Called to process a token.- Overrides:
visitToken
in classAbstractCheck
- Parameters:
ast
- the token to process
-
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
-