Double a()=new Double(25);

Question

what is the total memory occupied by this array statement

Answer 1

I would say zero. Your code is not working.
You declare a simple variable a type Double.
If you want a varible:
Double a = new Double(25);
And if you want and array of 25 elements:
Double[] a = new Double[25];
And to know the size just need to check on you JVM