EXP02-J. Use the two-argument Arrays.equals() method to compare the contents of arrays

Arrays fail to override class Object's equals() method; the implementation of the equals() method applied to arrays compares the array references rather than the contents of the arrays. Use the two-argument Arrays.equals() method to compare the contents of arrays. When intentionally testing reference equality, prefer the reference equality operators, == and !=; inappropriate use of the equals() method may lead to unexpected results.

Noncompliant Code Example

This noncompliant code example incorrectly uses the Object.equals() method to compare two arrays.

int[] arr1 = new int[20]; // initialized to 0
int[] arr2 = new int[20]; // initialized to 0
arr1.equals(arr2); // false

Compliant Solution

This compliant solution compares the two arrays using the two-argument Arrays.equals() method.

int[] arr1 = new int[20]; // initialized to 0
int[] arr2 = new int[20]; // initialized to 0
Arrays.equals(arr1, arr2); // true

Risk Assessment

Using the equals() method or relational operators when intending to compare array contents produces incorrect results, which may lead to vulnerabilities.

Automated Detection

The Coverity Prevent Version 5.0 BAD_EQ checker can detect the instance where The "==" operator is being used for equality of objects when in ideal case equal method should have been used. The "==" operator may consider objects different when the equals method considers them the same.

Static detection of attempts to use array_object.equals(...) appears to be straightforward.

Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this guideline on the CERT website.

Bibliography

[[API 2006]] Class Arrays

EXP01-J. Do not confuse abstract object equality with reference equality      04. Expressions (EXP)      EXP03-J. Avoid the equal and not equal operators when comparing boxed primitives