Writing Calculator Program in Swing
In this tutorial we are providing you an example which illustrates you how to
a create calculator in Swing with the source code and screen shot.
For developing a small calculator program in swing we need two different
classes
1) SwingCalculator.java
2) Calculator.java
The SwingCalculator.java calls the Calculator.java class by
JFrame frame = new Calculator(). All the
methods and actions are to be performed in Calculator.java class.
Calculator Code in Java Swing
Please save the code as SwingCalculator.java
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
class SwingCalculator {
public static void main(String[] args) {
JFrame frame = new Calculator();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}
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Here is the code of Calculator.java
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
class Calculator extends JFrame {
private final Font BIGGER_FONT = new Font("monspaced",
Font.PLAIN, 20);
private JTextField textfield;
private boolean number = true;
private String equalOp = "=";
private CalculatorOp op = new CalculatorOp();
public Calculator() {
textfield = new JTextField("0", 12);
textfield.setHorizontalAlignment(JTextField.RIGHT);
textfield.setFont(BIGGER_FONT);
ActionListener numberListener = new NumberListener();
String buttonOrder = "1234567890 ";
JPanel buttonPanel = new JPanel();
buttonPanel.setLayout(new GridLayout(4, 4, 4, 4));
for (int i = 0; i < buttonOrder.length(); i++) {
String key = buttonOrder.substring(i, i+1);
if (key.equals(" ")) {
buttonPanel.add(new JLabel(""));
} else {
JButton button = new JButton(key);
button.addActionListener(numberListener);
button.setFont(BIGGER_FONT);
buttonPanel.add(button);
}
}
ActionListener operatorListener = new OperatorListener();
JPanel panel = new JPanel();
panel.setLayout(new GridLayout(4, 4, 4, 4));
String[] opOrder = {"+", "-", "*", "/","=","C"};
for (int i = 0; i < opOrder.length; i++) {
JButton button = new JButton(opOrder[i]);
button.addActionListener(operatorListener);
button.setFont(BIGGER_FONT);
panel.add(button);
}
JPanel pan = new JPanel();
pan.setLayout(new BorderLayout(4, 4));
pan.add(textfield, BorderLayout.NORTH );
pan.add(buttonPanel , BorderLayout.CENTER);
pan.add(panel , BorderLayout.EAST );
this.setContentPane(pan);
this.pack();
this.setTitle("Calculator");
this.setResizable(false);
}
private void action() {
number = true;
textfield.setText("0");
equalOp = "=";
op.setTotal("0");
}
class OperatorListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
if (number) {
action();
textfield.setText("0");
} else {
number = true;
String displayText = textfield.getText();
if (equalOp.equals("=")) {
op.setTotal(displayText);
} else if (equalOp.equals("+")) {
op.add(displayText);
} else if (equalOp.equals("-")) {
op.subtract(displayText);
} else if (equalOp.equals("*")) {
op.multiply(displayText);
} else if (equalOp.equals("/")) {
op.divide(displayText);
}
textfield.setText("" + op.getTotalString());
equalOp = e.getActionCommand();
}
}
}
class NumberListener implements ActionListener {
public void actionPerformed(ActionEvent event) {
String digit = event.getActionCommand();
if (number) {
textfield.setText(digit);
number = false;
} else {
textfield.setText(textfield.getText() + digit);
}
}
}
public class CalculatorOp {
private int total;
public CalculatorOp() {
total = 0;
}
public String getTotalString() {
return ""+total;
}
public void setTotal(String n) {
total = convertToNumber(n);
}
public void add(String n) {
total += convertToNumber(n);
}
public void subtract(String n) {
total -= convertToNumber(n);
}
public void multiply(String n) {
total *= convertToNumber(n);
}
public void divide(String n) {
total /= convertToNumber(n);
}
private int convertToNumber(String n) {
return Integer.parseInt(n);
}
}
}
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The constructor new CalculatorOp() calls the CalculatorOp
class. The Swing
component JTextField is used to create textbox on which calculation is to be
performed. JPanel arranges the numeric buttons in a panel. JButton is used to
perform an action. OperatorListener class is called to perform action on
operators, i.e, '+,-,*,/,='. The class NumberListener is called for numbers 0 to
9.
Output will be displayed as:
Download Source Code
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