Issue with Apache Commons Complex add() function

Question

So basically I am writing an android app and I notice that the add function is not working properly. When I tried testing it with

Complex dummy = Complex.ZERO;
        dummy.add(Complex.I);
        Log.i("DEBUG", "DUMMY = " + dummy);

I get

I/DEBUG: DUMMY = (0.0, 0.0)

from Logcat. I can't seem to find what went wrong with such a simple function call.

This is the description of the function from Apache's website

public Complex add(Complex addend) throws NullArgumentException

Returns a Complex whose value is (this + addend). Uses the definitional formula (a + bi) + (c + di) = (a+c) + (b+d)i

Answer 1

Complex.Zero = (0.0 + 0.0i)

Complex.I = (0.0 + 1.0i)

Why not?

The answer is in your question itself(on the docs),

Returns a Complex whose value is (this + addend)

Here dummy.add(Complex.I); returns (0.0 + 1.0i) but is not used. So, assign the return value back to dummy

Correct code would be

dummy = dummy.add(Complex.I);

PS: Also, in my 5+ years of coding. I've blindly trusted Apache Commons everyday everytime. Never it failed ;)