GUI keeps compounding discount when I toggle JCheckBox - user-interface

Question

I am trying to make a GUI that when you click on one of two radio buttons, it will apply a different discount depending on whether you are a new customer or a returning customer. The discount is to be applied to each different option that you can choose. My problem is that everytime I click on the checkbox to add the option, it keeps compounding the discount. The first time it is right, but every click after it makes the discount higher and higher. Here is my code for the checkbox:
#FXML
void tires(ActionEvent event) {
if(isNewCustomer==true){
tireRotation=tireRotation*(1.0-newCustomerDiscount);
//costLabel.setText("$ " +DF.format(cost));
}else{
tireRotation=tireRotation*(1.0-regularCustomerDiscount);
// costLabel.setText("$ " +DF.format(cost));
}
if(tireBox.isSelected()){
cost+=tireRotation;
costLabel.setText("$ " +DF.format(cost));
} else {
cost =cost-tireRotation;
costLabel.setText("$ " +DF.format(cost));
}
}
Here is my code for the radio button:
#FXML
void newCustomer(ActionEvent event) {
if (newCustomer.isSelected()){
isNewCustomer=true;
}
}
Any help would be greatly appreciated!

Answer 1

I just reread you question. Create global variables. In your toggle box methods set the finalCost global variable.
Setting variable within if example:
global variables:
double finalCost = 0;
double initialCharge = 200;
double discount= 50;
double newAccountDiscount= 25;
first method:
if(tireBox.isSelected() && newCustomer.isSelected())
{
finalCost = initialCharge - discount - newAccountDiscount;
}
else if(tireBox.isSelected())
{
finalCost = initialCharge - discount;
}
else if(newCustomer.isSelected())
{
finalCost = initialCharge - newAccountDiscount;
}
else
{
finalCost = initalCharge;
}
second method:
if(tireBox.isSelected() && newCustomer.isSelected())
{
finalCost = initialCharge - discount - newAccountDiscount;
}
else if(tireBox.isSelected())
{
finalCost = initialCharge - discount;
}
else if(newCustomer.isSelected())
{
finalCost = initialCharge - newAccountDiscount;
}
else
{
finalCost = initalCharge;
}