nf.setMaximumFractionDigits(2);
}
/* User pressed Enter on a text field or
pressed Compute. Display the result if all
fields are completed. */
public void actionPerformed(ActionEvent ae) {
double result = 0.0;
String
amountStr
= amountText.getText();
String
periodStr
= periodText.getText();
String
rateStr =
rateText.getText();
String
compStr =
compText.getText();
try {
if(amountStr.length() != 0 &&
periodStr.length() != 0 &&
rateStr.length() != 0 &&
compStr.length() != 0) {
principal = Double.parseDouble(amountStr);
numYears = Double.parseDouble(periodStr);
rateOfRet = Double.parseDouble(rateStr) / 100;
compPerYear = Integer.parseInt(compStr);
result = compute();
futvalText.setText(nf.format(result));
}
showStatus(""); // erase any previous error message
} catch (NumberFormatException exc) {
showStatus("Invalid Data");
futvalText.setText("");
}
}
// Compute the future value.
double compute() {
double b, e;
b = (1 + rateOfRet/compPerYear);
e = compPerYear * numYears;
return principal * Math.pow(b, e);
}
}
Finding the Initial Investment Required to Achieve a Future Value
Sometimes you will want to know how large an initial investment is required to achieve
some future value. For example, if you are saving for your child's college education and
you know that you will need $75,000 in five years, how much money do you need to invest
at 7 percent to reach that goal? The InitInv applet developed here can answer that question.
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