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ID

CWE-581: Object Model Violation: Just One of Equals and Hashcode Defined

Weakness ID: 581
Abstraction: Base
Status: Draft
Presentation Filter:
+ Description

Description Summary

The software does not maintain equal hashcodes for equal objects.

Extended Description

Java objects are expected to obey a number of invariants related to equality. One of these invariants is that equal objects must have equal hashcodes. In other words, if a.equals(b) == true then a.hashCode() == b.hashCode().

+ Time of Introduction
  • Implementation
+ Applicable Platforms

Languages

Java

+ Common Consequences
ScopeEffect
Integrity
Other

Technical Impact: Other

If this invariant is not upheld, it is likely to cause trouble if objects of this class are stored in a collection. If the objects of the class in question are used as a key in a Hashtable or if they are inserted into a Map or Set, it is critical that equal objects have equal hashcodes.

+ Potential Mitigations

Phase: Implementation

Both Equals() and Hashcode() should be defined.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness ClassWeakness Class573Improper Following of Specification by Caller
Development Concepts (primary)699
Research Concepts (primary)1000
ChildOfCategoryCategory850CERT Java Secure Coding Section 05 - Methods (MET)
Weaknesses Addressed by the CERT Java Secure Coding Standard (primary)844
ChildOfCategoryCategory977SFP Secondary Cluster: Design
Software Fault Pattern (SFP) Clusters (primary)888
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
CERT Java Secure CodingMET09-JClasses that define an equals() method must also define a hashCode() method
+ Content History
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Potential_Mitigations, Time_of_Introduction
2008-09-08CWE Content TeamMITREInternal
updated Common_Consequences, Relationships, Other_Notes
2009-10-29CWE Content TeamMITREInternal
updated Common_Consequences, Description, Other_Notes
2010-12-13CWE Content TeamMITREInternal
updated Common_Consequences
2011-03-29CWE Content TeamMITREInternal
updated Description
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences, Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2012-10-30CWE Content TeamMITREInternal
updated Potential_Mitigations
2014-07-30CWE Content TeamMITREInternal
updated Relationships
Previous Entry Names
Change DatePrevious Entry Name
2008-01-30Object Model Violation: Just One of Equals and Haschode Defined

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Page Last Updated: May 05, 2017