Finding specific data's index on an array

Question

Hi,
I have an array with 100 members like below. But I dont know the members because its dynamically coming from a DB.

staticIntArray[0] = 1;
staticIntArray[1] = 434;
staticIntArray[2] = 555;
...

The question is, I want learn that what is the index number of "555"? Is there any propery for arrays?