我正在编写一个简单的程序，以便在Money Time of Money上获得乐趣，并且遇到了将我的变量calc发布到calculateTF TextField中的问题。
import java.util.Scanner;
import java.awt.event.*;
import java.awt.*;
import javax.swing.*;
// The time value of money (TVM) is the idea that money available at the present time
// is worth more than the same amount in the future due to its potential earning capacity.
// FV = Future value of money
// PV = Present value of money
// i = interest rate
// n = number of compounding periods per year
// t = number of years
// FV = PV x (1 + (i / n))^(n x t)
public class timeValue2 extends JFrame {
private static final int WIDTH = 400;
private static final int HEIGHT = 300;
private JLabel futureValue, presentValue, interestRate, periods, years, payment;
private JTextField futureValueTF, presentValueTF, interestRateTF, periodsTF, yearsTF, paymentTF, calculateTF;
private JButton calculateB, exitB;
private CalculateButtonHandler cbHandler;
private ExitButtonHandler ebHandler;
public timeValue2() {
// Labels
futureValue = new JLabel("Enter the future value: ", SwingConstants.RIGHT);
presentValue = new JLabel("Enter the present value: ", SwingConstants.RIGHT);
interestRate = new JLabel("Enter I/Y: ", SwingConstants.RIGHT);
periods = new JLabel("Enter periods: ", SwingConstants.RIGHT);
years = new JLabel("Enter years: ", SwingConstants.RIGHT);
payment = new JLabel("Enter payment: ", SwingConstants.RIGHT);
// Text Fields
futureValueTF = new JTextField(10);
presentValueTF = new JTextField(10);
interestRateTF = new JTextField(10);
periodsTF = new JTextField(10);
yearsTF = new JTextField(10);
paymentTF = new JTextField(10);
calculateTF = new JTextField(10);
// Buttons
calculateB = new JButton("Calculate");
cbHandler = new CalculateButtonHandler();
calculateB.addActionListener(cbHandler);
exitB = new JButton("Exit");
ebHandler = new ExitButtonHandler();
exitB.addActionListener(ebHandler);
setTitle("Time-Value of Money");
Container pane = getContentPane();
pane.setLayout(new GridLayout(4, 2));
pane.add(futureValue);
pane.add(futureValueTF);
pane.add(presentValue);
pane.add(presentValueTF);
pane.add(interestRate);
pane.add(interestRateTF);
pane.add(payment);
pane.add(paymentTF);
pane.add(periods);
pane.add(periodsTF);
pane.add(years);
pane.add(yearsTF);
pane.add(calculateB);
pane.add(calculateTF);
pane.add(exitB);
setSize(WIDTH, HEIGHT);
setVisible(true);
setDefaultCloseOperation(EXIT_ON_CLOSE);
}
private class CalculateButtonHandler implements ActionListener {
public void actionPerformed(ActionEvent e) {
// Here the .getText() operator gets the text from TF pane's.
double futureValue, presentValue, interestRate, periods, years, calc, payment;
String fv, pv, ir, p, y, pmt;
fv = futureValueTF.getText();
pv = presentValueTF.getText();
ir = interestRateTF.getText();
p = periodsTF.getText();
y = yearsTF.getText();
pmt = paymentTF.getText();
futureValue = Double.parseDouble(fv);
presentValue = Double.parseDouble(pv);
interestRate = Double.parseDouble(ir);
periods = Double.parseDouble(p);
years = Double.parseDouble(y);
payment = Double.parseDouble(pmt);
// Now I need to perform the TVM operations.
// What I need is a document listener
if(fv.isEmpty()) {
calc = presentValue * Math.pow((1 + (interestRate / years)), (years * periods));
calculateTF.setText("" + calc);
} else if(pv.isEmpty()) {
calc = ((payment/interestRate) - futureValue) * (1/Math.pow((1 + interestRate), years)) - (payment / interestRate);
calculateTF.setText("" + calc);
} else if(ir.isEmpty()) {
calc = (presentValue * Math.pow((1 + interestRate), years)) + (payment * ((Math.pow((1 + interestRate), years) - 1)/interestRate)) + futureValue;
calculateTF.setText("" + calc);
} else if(p.isEmpty()) {
calc = (presentValue * Math.pow((1 + interestRate),periods)) + (payment * (((Math.pow((1 + interestRate),periods)) - 1)/interestRate)) + futureValue;
calculateTF.setText("" + calc);
} else if(pmt.isEmpty()) {
calc = (presentValue + ((presentValue + futureValue)/(Math.pow((1 + interestRate),periods) - 1) * (-interestRate / 1)));
calculateTF.setText("" + calc);
}
// The .setText() operator sets the text in the (yet to be created) calculate box.
}
}
public class ExitButtonHandler implements ActionListener {
public void actionPerformed(ActionEvent e) {
System.exit(0);
}
}
public static void main(String[] args) {
timeValue2 boss = new timeValue2();
}
}
运行时，代码会调出用户界面并允许用户输入数据，但显然计算没有运行或者值没有放在TextField中。