How to summation in java?

[km2011]

Hello everyone, i want to do the summation below:

x1= a0x0
x2= x1+ a1x1
x3= x1 + x2 + a2*x2 and so on............

supose we know x0 = 2; a0=1 ; a1 = 3; a2 = 2;

how do i use for loop to do this?
should i keep it in array?

thanks inadvance

[stultuske]

how do you seperate your different parts? is there always a space between the 'value' and the operators or not?

[Aviras]

What you can do for instance is put all your coefficients (aka a0,a1, etc) in an array, then make a for loop through that array.

Just keep a value say x, and every time you enter the for loop, add x+ai*x

EDIT: Didn't read your third line for the summation thoroughly, instead of adding x+aix, you get in fact (n-1)x1+(n-2)a1x1+(n-3)a2*x2 etc, just write the full sum down for say x4 and you'll see what I mean, the approach is the same, the formula just changes a bit. Or you could just put all the x's in a different array as well, and then in the for loop, also loop through the previous x's

[JamesCherrill]

Although you can look at the iterative definition and convert it to an explicit formula, this gives a solution, no matter how efficient, that hides rather than exposes the original definition. For that reason I would go with the second approach - two arrays, x and a. Array a must be fully populated, and x[0] must be given a value, then you can have a simple loop that fills in the remaining values for the x array.

[km2011]

Thanks so much sir .it's really useful ^_^