# V6013. Comparison of arrays, strings, collections by reference. Possibly an equality comparison was intended.

Analyzer has detected a situation where srtings/arrays/collections are compared using the operator '=='. Most likely comparison of content was implied and actually a direct comparison of object references is taking place.

Let's look at the example of incorrect comparison of strings:

    if (str1 == "example") {}
    if (str1 == str2) {}

In these cases, if the contents of ' str1 ' and ' str2 ' are identical and are equal to "example", then conditions will be false, because the '==' operator compares the addresses of objects, and not the contents of strings. If it is required to compare strings by content, the correct variant of the code will look like as follows:

    if (str1.equals("example")) {}
    if (str1.equals(str2)) {}

Let's look at the example of incorrect comparison of arrays:

    int[] a = ...;
    int[] b = ...;
    ...
    if (a.equals(b)) { ... }

For arrays, the call of method 'equals' is the same as the '==' operator. The object addresses are compared, not the content. In order to compare arrays by content, you must rewrite the code as follows:

    if (Arrays.equals(a ,b){ ... }

The operator '==' behaves the same way both with collections, arrays and strings.

This diagnostic is classified as:

CWE-595 CERT-EXP03-J

You can look at examples of errors detected by the V6013 diagnostic.