You need to calculate it with following iteration:
double result = 0;
Integer [] nums = coefficients.toArray(new Integer[0]);
for(int i = 0; i < nums.length; i++){
result = result *x + nums[i];
}
System.out.println(result);
It is known as Horner's method. The benefit of this approach for example of fourth degree of polynomial is:
f(x) = ax^3 + bx^2 + cx + z
is transformed to:
f(x) = ((a)*x + b)*x + c)*x + z