Comparison of Object References Instead of Object Contents
Weakness ID: 595 (Weakness Base)Status: Incomplete
+ Description

Description Summary

The program compares object references instead of the contents of the objects themselves, preventing it from detecting equivalent objects.
+ Time of Introduction
  • Implementation
+ Demonstrative Examples

Example 1

In the following example, two Truck objects are compared using the == operator (incorrect) as opposed to calling the equals() method (correct).

(Bad Code)
Example Language: Java 
public boolean compareTrucks(Truck a, Truck b) {
return a == b;
}
+ Potential Mitigations

Use the equals() method to compare objects instead of the == operator. If using ==, it is important for performance reasons that your objects are created by a static factory, not by a constructor.

+ Other Notes

This problem can cause unexpected application behavior. Comparing objects using == usually produces deceptive results, since the == operator compares object references rather than values. To use == on a string, the programmer has to make sure that these objects are unique in the program, that is, that they don't have the equals method defined or have a static factory that produces unique objects.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfCategoryCategory171Cleansing, Canonicalization, and Comparison Errors
Development Concepts699
ChildOfCategoryCategory569Expression Issues
Development Concepts (primary)699
ChildOfWeakness ClassWeakness Class697Insufficient Comparison
Research Concepts (primary)1000
ParentOfWeakness VariantWeakness Variant597Use of Wrong Operator in String Comparison
Development Concepts (primary)699
Research Concepts (primary)1000
+ Content History
Modifications
Modification DateModifierOrganizationSource
2008-07-01Sean EidemillerCigitalExternal
added/updated demonstrative examples
2008-07-01Eric DalciCigitalExternal
updated Time of Introduction
2008-09-08CWE Content TeamMITREInternal
updated Description, Relationships, Other Notes
2009-05-27CWE Content TeamMITREInternal
updated Name
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Incorrect Object Comparison: Syntactic
2009-05-27Incorrect Syntactic Object Comparison
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