WHAT IS WRONG??!?!? unknown error

so.... here is a molar mass calculator... it only needs to find the molar mass with C,H,N,O. please help
import java.util.Scanner;
/**
* Cookin' some chicken.
*
* @
* @1.1
*/

public class FormulaMass
{
final static double Carbon = 12.0107;
final static double Oxygen = 15.9994;
final static double Nitrogen = 14.0067;
final static double Hydrogen = 1.00794;
String formula;
String [] formarray;
double Product;
int x;
int y;
int numletters;
int q;
int e;
int f;
double g;


public FormulaMass()
{
getInput();
arrayConstructor();
calculations();
output();

}
public void getInput()
{
Scanner in = new Scanner (System.in);
System.out.println("Enter the formula of your carbon, oxygen,nitrogen or hydrogen compound: ");
formula = in.next();
}
private String arrayConstructor()
{
for (x=0; x< formula.length(); x++)
{
numletters++;
}
String [] subscript = new String[numletters];
formarray = subscript;
return formarray[numletters];
}
private double calculations()
{
for (x =0; x<=formula.length(); x++)
{
if (formarray[x].equals ("C"))
{
q = Integer.parseInt(formarray[x+1]);
Product = Product + (q * Carbon);
}
if (formarray[x].equals ("N"))
{
q = Integer.parseInt(formarray[x+1]);
Product = Product + (q * Nitrogen);
}
if (formarray[x].equals ("H"))
{
q = Integer.parseInt(formarray[x+1]);
Product = Product + (q * Hydrogen);
}
if (formarray[x].equals ("O"))
{
q = Integer.parseInt(formarray[x+1]);
Product = Product + (q * Oxygen);
}
else
{
e = Integer.parseInt(formarray[x]);
f = Integer.parseInt(formarray[x-1]);
if (formarray[x+2].equals ("C"))
{
g = Carbon;
}
if (formarray[x+2].equals ("N"))
{
g = Nitrogen;
}
if (formarray[x+2].equals ("H"))
{
g = Hydrogen;
}
if (formarray[x+2].equals ("O"))
{
g = Oxygen;
}
else
{
g = 0;
}
f = (f * 10) - f;
Product = Product + (e * g) + (g * f);
}
}
return Product;
}
public void output ()
{
System.out.println(Product);
}
}

?!?!?! anything?

Please use the HIGHLIGHT tags to make it easier for us to read your code. Also, please be specific about what you are having problems with.

From what I can see; you are asking for the input but not using it. Try returning a value in the getInput() method. Also, where is the entry point to the program? I cannot see a main function.