Java The Complete Reference, Seventh Edition

Chapter 32: Financial Applets and Servlets 951

fields are completed. */

public void actionPerformed(ActionEvent ae) {

double result = 0.0;

String regWDStr = regWDText.getText();

String periodStr = periodText.getText();

String rateStr = rateText.getText();

String numWDStr = numWDText.getText();

try {

if(regWDStr.length() != 0 &&

periodStr.length() != 0 &&

rateStr.length() != 0 &&

numWDStr.length() != 0) {

regWDAmount = Double.parseDouble(regWDStr);

numYears = Double.parseDouble(periodStr);

rateOfRet = Double.parseDouble(rateStr) / 100;

numPerYear = Integer.parseInt(numWDStr);

result = compute();

initialText.setText(nf.format(result));

}

showStatus(""); // erase any previous error message

} catch (NumberFormatException exc) {

showStatus("Invalid Data");

initialText.setText("");

}

}

// Compute the required initial investment.

double compute() {

double b, e;

double t1, t2;

t1 = (regWDAmount * numPerYear) / rateOfRet;

b = (1 + rateOfRet/numPerYear);

e = numPerYear * numYears;

t2 = 1 - (1 / Math.pow(b, e));

return t1 * t2;

}

}

Finding the Maximum Annuity for a Given Investment

Another annuity calculation computes the maximum annuity (in terms of a regular withdrawal)

available from a given investment over a specified period of time. For example, if you have