Remove duplicates from a large integer array using Java

Do you know of any time efficient way to remove duplicated values from a very big integer array using Java? The size of the array depends on the logged in user, but will always exceed 1500000 unsorted values with some duplicates. Every integer contains a number between 100000 and 9999999.

I tried converting it to a List, but the heap on my server doesn't allow this amount of data(my ISP has restricted it). And a regular for loop within a for loop takes over 5 minutes to calculate.

The size of the array without the duplicates is the one I will store in my database.

Help would be appreciated!