public void actionPerformed(ActionEvent event) {
final Object item = fieldMortgageChoices.getSelectedItem();
if (item instanceof Mortgage) {
final Mortgage mortgageTerms = (Mortgage) item;
// update the fields, but tell the document listener to
// not react to those changes since we don't want the
// combo box to then be changed in turn
ignoreDocumentChange = true;
fieldRate.setText(FMT_RATE.format(mortgageTerms.getRate()));
fieldTerm.setText(FMT_TERM.format(mortgageTerms.getTerm()));
ignoreDocumentChange = false;
}
}
/**
* Utility method that will calculate a new mortgage payment and payment breakdown based on the
* user's current selection.
*/
private void calculateMortgage() {
boolean inputValid = true;
// fetch the new values from the data entry fields and calculate a
// new mortgage
double principal = 0.0;
try {
final String principalText = fieldPrincipal.getText();
principal = FMT_PRINCIPAL.parse(principalText).doubleValue();
if (principal <= 0.0) {
invalidInput(fieldPrincipal, MSG_PRINCIPAL_NEGATIVE);
inputValid = false;
}
} catch (ParseException ex) {
invalidInput(fieldPrincipal, MSG_INVALID_INPUT);
inputValid = false;
}
double rate = 0.0;
if (inputValid) {
try {
final String rateText = fieldRate.getText();
rate = FMT_RATE.parse(rateText).doubleValue();
if (rate <= 0.0) {
invalidInput(fieldRate, MSG_RATE_NEGATIVE);
inputValid = false;
}
} catch (ParseException ex) {
invalidInput(fieldRate, MSG_INVALID_INPUT);
inputValid = false;
}
}
int term = 0;
if (inputValid) {
try {
final String termText = fieldTerm.getText();
term = FMT_TERM.parse(termText).intValue();
if (term <= 0) {
invalidInput(fieldTerm, MSG_TERM_NEGATIVE);
inputValid = false;
}
} catch (ParseException ex) {
invalidInput(fieldTerm, MSG_INVALID_INPUT);
inputValid = false;
}
}
if (inputValid) {
// create a new Mortgage object from the selected mortgage terms and
// then update the principal with the user's requested value
final Mortgage mortgage = new Mortgage(principal, rate, term);
// format the mortgage payment into a user-friendly message
final Object[] values = {new Double(mortgage.getPayment())};
final String message = MessageFormat.format(MSG_PAYMENT, values);
// update our message label and payment data and force our UI
// to repaint itself with the new mortgage results
labelMessage.setText(message);
paymentsModel.setPayments(mortgage.getPayments());
// create a data set so the chart may be updated with the mortgage
// payment detail
final MortgagePayment[] payments = mortgage.getPayments();
final double[][] chartData = new double[2][payments.length];
for (int i = 0; i < payments.length; i++) {
chartData[0][i] = payments[i].getInterest().doubleValue();
chartData[1][i] = payments[i].getPrincipal().doubleValue();
}
final String[] chartDataNames = {"Interest", "Principal"};
final NumberFormat[] formats = {new DecimalFormat("#,##0"), new DecimalFormat("$ #,##0.00")};
paymentsChart.setData(chartData, chartDataNames, formats);
repaint();
}
}