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Equals on incomparable types

ID: java/equals-on-unrelated-types Kind: problem Security severity: Severity: error Precision: very-high Tags: - quality - reliability - correctness - external/cwe/cwe-571 Query suites: - java-code-quality.qls - java-security-and-quality.qls

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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