I'm brand new to java (college class), and have a quick question. Instead of outputting the correct numbers to the Applet, it just lists each one as "0.0". What am I doing wrong? Thank you.

P.S. I know I need to clean the code up a lot and make some other major changes, but I just need help on this particular problem at the moment.

import javax.swing.*;
import java.awt.Graphics;
import java.applet.*;

public class GDPmodel extends Applet {

double GDP,GDPVal, TaxChange, MPC1, RChange, GChange1, NXC;
double initialGDP;


// Contructor

public GDPmodel()
{

}

public GDPmodel(double initGDP)
{
GDP = initGDP;
initialGDP = initGDP;
}


// Methods
public void NX (double NXchange)
{
NXC = NXchange;
GDP = GDP + NXchange;
}

public void G (double Gchange)
{
GChange1 = Gchange;
GDP = GDP + Gchange;
}

public void I (double R)
{
RChange = R;
GDP = GDP - ((initialGDP/4)*(R/100));
}

public void C (double T, double MPC)
{
TaxChange = T;
MPC1 = MPC;
GDP = GDP+ ((MPC*initialGDP) * (initialGDP-(T*initialGDP)));
}


public void init ()
//public static void main(String[] args)
{

double GDPVal, TaxChange, MPC, RChange, GChange, Import, Export = 0;
String InitGDPVal, TaxVal, MPCVal, RVal, GVal, ImportVal, ExportVal;

// Input values

InitGDPVal = JOptionPane.showInputDialog("Enter initial GDP value in billions of dollars (to default to actual 2005 GDP, enter 0):" );
TaxVal = JOptionPane.showInputDialog("Enter percentage change in tax rate:" );
MPCVal = JOptionPane.showInputDialog("Enter the marginal propensity to consume:" );
RVal = JOptionPane.showInputDialog("Enter the change in interest rate in percentage terms:" );
GVal = JOptionPane.showInputDialog("Enter change in government spending in dollars:" );
ImportVal = JOptionPane.showInputDialog("Enter change in dollar value of imports:" );
ExportVal = JOptionPane.showInputDialog("Enter change in dollar value of exports:" );

//Convert from a String to a double

GDPVal = Double.parseDouble(InitGDPVal);
TaxChange = Double.parseDouble(TaxVal);
MPC = Double.parseDouble(MPCVal);
RChange = Double.parseDouble(RVal);
GChange = Double.parseDouble(GVal);
Import = Double.parseDouble(ImportVal);
Export = Double.parseDouble(ExportVal);

if(GDPVal == 0.0)
{
GDPVal = 12370; //12.37 trillion is 2005 estimate from CIA factbook using PPP
} else {}

GDPmodel model = new GDPmodel(GDPVal);

model.NX(Export-Import);
model.G(GChange);
model.I(RChange);
model.C(TaxChange, MPC);

}

public void paint (Graphics g){

super.paint(g);

g.drawRect(15, 10, 400, 155);

g.drawString("You entered an initial GDP of $ " + initialGDP + " billion.", 25, 25);
g.drawString("You entered a tax percentage change of " + TaxChange + "%.", 25, 45);
g.drawString("You entered a marginal propensity to consume of " + MPC1 + ".", 25, 65);
g.drawString("You entered an interest rate change of " + RChange, 25, 85);
g.drawString("You entered a change in government spending of $" + GChange1 + " billion.", 25, 105);
g.drawString("You entered a net export change of $ " + NXC + " billion.", 25, 125);
g.drawString("Your new GDP is $ " + GDP + " billion.", 25, 145);

}

}