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Writing Calculator Program in Swing
Posted on: September 12, 2008 at 12:00 AM

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.

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);

  }

}

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);

  }

}

      }

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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