Computer Science Programming Tutorials
Java Simple Interest Calculator
In Java

Java GUI Simple Interest Calculator

1 Min Read

Simple Java GUI Calculator that performs simple interest calculation.

GUI Simple Interest Calculator using Java
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import java.awt.*;
import java.awt.event.*;
import java.awt.event.ActionListener;
import javax.swing.*;
import javax.swing.border.TitledBorder;
 
public class ModifiedGUISimpleInterestCalculator extends JFrame {
    //create TextFields for principal, rate and time
 
    private JTextField principal = new JTextField();
    private JTextField rate = new JTextField();
    private JTextField time = new JTextField();
    private JTextField simpleInterest = new JTextField();
    // calculate JButton
    private JButton clear = new JButton("Clear");
    private JButton calculate = new JButton("Calculate");
    //private JButton clear = new JButton("Clear");
    //create JTextArea
    JTextArea area = new JTextArea(1, 1);
 
    public ModifiedGUISimpleInterestCalculator() {
        // panel panel to hold labels and text fields
        JPanel panel1 = new JPanel(new GridLayout(5, 2));
        panel1.add(new JLabel("Enter Principal"));
        panel1.add(principal);
        panel1.add(new JLabel("Enter Rate"));
        panel1.add(rate);
        panel1.add(new JLabel("Enter Time"));
        panel1.add(time);
        panel1.add(new JLabel("Simple Interest"));
        panel1.add(simpleInterest);
        panel1.setBorder(new TitledBorder("Enter Principal, Rate (as decimal e.g 0.1 for 10%) and Time."));
 
        principal.setBorder(BorderFactory.createEtchedBorder());
        rate.setBorder(BorderFactory.createEtchedBorder());
        time.setBorder(BorderFactory.createEtchedBorder());
        simpleInterest.setBorder(BorderFactory.createEtchedBorder());
        simpleInterest.setEditable(false);
        simpleInterest.setForeground(Color.RED);
 
        // Panel p2 to hold the button
        JPanel panel2 = new JPanel(new FlowLayout(FlowLayout.RIGHT));
 
        //panel2.add(clear);
        panel2.add(clear);
        panel2.add(calculate);
 
        // Add the panels to the frame
        add(panel1, BorderLayout.CENTER);
        add(panel2, BorderLayout.SOUTH);
 
        area.setForeground(Color.BLACK);
        area.setBackground(Color.WHITE);
        area.setLineWrap(true);
        area.setWrapStyleWord(true);
        area.setEditable(false);
 
        calculate.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                // Get values from text fields
                try {
                    double amount = Double.parseDouble(principal.getText());
                    double rateOfInterest = Double.parseDouble(rate.getText());
                    double year = Double.parseDouble(time.getText());
 
 
 
                    String interest = "" + (amount * rateOfInterest * year);
                    // Display simple interest
                    simpleInterest.setText((interest));
                } catch (Exception f) {
                    JOptionPane.showMessageDialog(rootPane, "ERROR: " + (f.getMessage()));
                }
 
                String amountField = principal.getText();
                String rateOfInterestField = rate.getText();
                String yearField = time.getText();
 
                if (e.getSource() == calculate) {
 
                    if ("".equals(amountField) || "".equals(rateOfInterestField) || "".equals(yearField)) {
                        String emptyFieldWarning;
                        emptyFieldWarning = "One or more fields is/are empty!";
                        JOptionPane.showMessageDialog(rootPane, emptyFieldWarning);
                    }
                }
            }
        });
 
        clear.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                // Get values from text fields
                try {
                    principal.setText("");
                    rate.setText("");
                    time.setText("");
                    simpleInterest.setText("");
                } catch (Exception f) {
                }
            }
        });
    }
    //create main method to run application
 
    public static void main(String[] args) {
 
        ModifiedGUISimpleInterestCalculator calculator = new ModifiedGUISimpleInterestCalculator();
        calculator.setSize(360, 200);
        calculator.setTitle(" Simple Interest Calculator ");
        calculator.setResizable(false);
        calculator.setVisible(true);
        calculator.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}

Below is a screenshot of the output when the program is run.  Click…

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