Is the method calls inside if-checks "tested" and then "reverted"?

Thanks for taking the time by checking out this question. I have suddenly forgotten how method calls inside if-checks works. See the example code below.

Example:

if (list.next() instanceof AClass) {
    AClass thing = list.next();
}

If next() iterates to the next object in a list, is the two list.next() items the same object?

Is the method calls inside if-checks "tested" and then "reverted" so the same method call in the body equals the same as the one in the if-check?

Thanks!