Equals on incomparable types¶
ID: java/equals-on-unrelated-types
Kind: problem
Security severity:
Severity: error
Precision: very-high
Tags:
- reliability
- correctness
Query suites:
- java-security-and-quality.qls
Click to see the query in the CodeQL repository
Calls of the form x.equals(y), where x and y have incomparable types, should always return false because the runtime types of x and y will be different. Two types are incomparable if they are distinct and do not have a common subtype.
Recommendation¶
Ensure that such comparisons use comparable types.
Example¶
In the following example, the call to equals on line 5 refers to the whole array by mistake, instead of a specific element. Therefore, “Value not found” is returned.
String[] anArray = new String[]{"a","b","c"}
String valueToFind = "b";
for(int i=0; i<anArray.length; i++){
if(anArray.equals(valueToFind){ // anArray[i].equals(valueToFind) was intended
return "Found value at index " + i;
}
}
return "Value not found";
References¶
Java API Specification: Object.equals().