Programming Tutorials

Calculator application in Java

By: Linda Ng in Java Tutorials on 2023-04-23  

This Java sample program is a calculator application.

This sample program uses Java Swing to display a calculation application. This program can be studied in detail to understand the basic Java constructs and Java Swing.

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.text.*; 
public class CalculatorApplication extends JFrame implements ActionListener {

    JTextField resultField;
	double operandOne;
	double operandTwo;
    int operator;

    JButton addButton;
    JButton subtractButton;
    JButton multiplyButton;
    JButton divideButton;
    JButton percentileButton;
    JButton equalsButton;
    JButton dotButton;
    JButton cancelButton;
    JButton onebyButton;
    JButton backButton;

    JButton one1;
    JButton two2;
    JButton three3;
    JButton four4;
    JButton five5;
    JButton six6;
    JButton seven7;
    JButton eight8;
    JButton nine9;
    JButton zero0;

    Object source;
    
    public static void main(String[] args) {

        CalculatorApplication app = new CalculatorApplication();
        app.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent we) {
                System.exit(0);
            }
        });

        app.setSize(280, 240);

        app.setVisible(true);
    }

    public CalculatorApplication() {

  
        super();
 

        JPanel operandPanel;
        JPanel buttonPanel1;
        JPanel buttonPanel2;
        JPanel buttonPanel3;
        JPanel buttonPanel4;
    
        Container cp;
    
        cp = getContentPane();
 
        cp.setLayout(new GridLayout(5, 1));

    
        operandPanel = new JPanel();
        operandPanel.setLayout(new FlowLayout());
        
        resultField = new JTextField("0", 23);
        resultField.setHorizontalAlignment(SwingConstants.RIGHT);

        operandPanel.add(resultField);
        cp.add(operandPanel);

  
        buttonPanel1 = new JPanel();
        buttonPanel1.setLayout(new FlowLayout());
        seven7 = new JButton(" 7 ");
        seven7.addActionListener(this);
        buttonPanel1.add(seven7);
        eight8 = new JButton(" 8 ");
        eight8.addActionListener(this);
        buttonPanel1.add(eight8);
        nine9 = new JButton(" 9 ");
        nine9.addActionListener(this);
        buttonPanel1.add(nine9);
        divideButton = new JButton(" / ");
        divideButton.addActionListener(this);
        buttonPanel1.add(divideButton);
        cancelButton = new JButton(" C ");
        cancelButton.addActionListener(this);
        buttonPanel1.add(cancelButton);
        cp.add(buttonPanel1);

        buttonPanel2 = new JPanel();
        buttonPanel2.setLayout(new FlowLayout());
        four4 = new JButton(" 4 ");
        four4.addActionListener(this);
        buttonPanel2.add(four4);
        five5 = new JButton(" 5 ");
        five5.addActionListener(this);
        buttonPanel2.add(five5);
        six6 = new JButton(" 6 ");
        six6.addActionListener(this);
        buttonPanel2.add(six6);
        multiplyButton = new JButton(" * ");
        multiplyButton.addActionListener(this);
        buttonPanel2.add(multiplyButton);
        backButton = new JButton(" B ");
        backButton.addActionListener(this);
        buttonPanel2.add(backButton);
        cp.add(buttonPanel2);


        buttonPanel3 = new JPanel();
        buttonPanel3.setLayout(new FlowLayout());
        one1 = new JButton(" 1 ");
        one1.addActionListener(this);
        buttonPanel3.add(one1);
        two2 = new JButton(" 2 ");
        two2.addActionListener(this);
        buttonPanel3.add(two2);
        three3 = new JButton(" 3 ");
        three3.addActionListener(this);
        buttonPanel3.add(three3);
        subtractButton = new JButton(" - ");
        subtractButton.addActionListener(this);
        buttonPanel3.add(subtractButton);
        onebyButton = new JButton("1/x");
        onebyButton.addActionListener(this);
        buttonPanel3.add(onebyButton);
        cp.add(buttonPanel3);

        buttonPanel4 = new JPanel();
        buttonPanel4.setLayout(new FlowLayout());
        zero0 = new JButton(" 0 ");
        zero0.addActionListener(this);
        buttonPanel4.add(zero0);
        dotButton = new JButton(" . ");
        dotButton.addActionListener(this);
        buttonPanel4.add(dotButton);
        percentileButton = new JButton(" % ");
        percentileButton.addActionListener(this);
        buttonPanel4.add(percentileButton);
        addButton = new JButton(" + ");
        addButton.addActionListener(this);
        buttonPanel4.add(addButton);
        equalsButton = new JButton(" = ");
        equalsButton.addActionListener(this);
        buttonPanel4.add(equalsButton);
        cp.add(buttonPanel4);

    }

    public void showResult() {
        boolean validOperands;
        DecimalFormat df = new DecimalFormat("0.00");

        try {
           // operandOne = Double.parseDouble(operandOneField.getText());
           // operandTwo = Double.parseDouble(operandTwoField.getText());
            validOperands = true;
        } catch(NumberFormatException nfe) {
            validOperands = false;
        }
  
        if (validOperands) {
            if (source == addButton) {
                operandOne =Double.parseDouble(resultField.getText());
		resultField.setText("0");
		operator = 1;
            }
            else if (source == subtractButton) {
             	operandOne =Double.parseDouble(resultField.getText());
		resultField.setText("0");
		operator = 2;
            }
            else if (source == multiplyButton) {
	        operandOne = Double.parseDouble(resultField.getText());
		resultField.setText("0");
		operator = 3;
            }
            else if (source == divideButton) {
             	operandOne = Double.parseDouble(resultField.getText());
		resultField.setText("0");
		operator = 4;
            }
            else if (source == percentileButton) {
             	operandOne =Double.parseDouble(resultField.getText());
		resultField.setText("0");
		operator = 5;
            }
            else if (source == equalsButton) {
             	operandTwo = Double.parseDouble(resultField.getText());
		switch(operator){
		case 1:
		resultField.setText(Double.toString(operandOne + operandTwo));
		operandOne = 0.0;
		operandTwo = 0.0;
		break;
		case 2:
		resultField.setText(Double.toString(operandOne - operandTwo));
		operandOne = 0.0;
		operandTwo = 0.0;
		break;
		case 3:
		resultField.setText(Double.toString(operandOne * operandTwo));
		operandOne = 0.0;
		operandTwo = 0.0;
		break;
		case 4:
                if (operandTwo != 0.0){
                   resultField.setText(Double.toString(operandOne / operandTwo));
		operandOne = 0.0;
		operandTwo = 0.0;}
                else{
                  resultField.setText("0");}
		break;
		case 5:
		resultField.setText(Double.toString(operandOne % operandTwo));
		operandOne = 0.0;
		operandTwo = 0.0;
		}

            }
	else if (source == onebyButton) {
		if (resultField.getText().equals("0"))
			resultField.setText("0");
		else
	resultField.setText(Double.toString(1.0 / Double.parseDouble(resultField.getText())));
	    }
	    else if (source == one1) {
		if (resultField.getText().equals("0"))
			resultField.setText("1");
		else
			resultField.setText(resultField.getText() + "1");
	    }
	else if (source == two2) {
		if (resultField.getText().equals("0"))
			resultField.setText("2");
		else
			resultField.setText(resultField.getText() + "2");
	    }
	else if (source == three3) {
		if (resultField.getText().equals("0"))
			resultField.setText("3");
		else
			resultField.setText(resultField.getText() + "3");
	    }
	else if (source == four4) {
		if (resultField.getText().equals("0"))
			resultField.setText("4");
		else
			resultField.setText(resultField.getText() + "4");
	    }
	else if (source == five5) {
		if (resultField.getText().equals("0"))
			resultField.setText("5");
		else
			resultField.setText(resultField.getText() + "5");
	    }
	else if (source == six6) {
		if (resultField.getText().equals("0"))
			resultField.setText("6");
		else
			resultField.setText(resultField.getText() + "6");
	    }
	else if (source == seven7) {
		if (resultField.getText().equals("0"))
			resultField.setText("7");
		else
			resultField.setText(resultField.getText() + "7");
	    }
	else if (source == eight8) {
		if (resultField.getText().equals("0"))
			resultField.setText("8");
		else
			resultField.setText(resultField.getText() + "8");
	    }
	else if (source == nine9) {
		if (resultField.getText().equals("0"))
			resultField.setText("9");
		else
			resultField.setText(resultField.getText() + "9");
	    }
	else if (source == zero0) {
		if (resultField.getText().equals("0"))
			resultField.setText("0");
		else
			resultField.setText(resultField.getText() + "0");
	    }
	else if (source == dotButton) {
		if (resultField.getText().equals("0"))
			resultField.setText("0.");
		else if (resultField.getText().indexOf('.') == -1){
			resultField.setText(resultField.getText() + ".");
		}
		else{}
			
	    }
	else if (source == cancelButton) {
		resultField.setText("0");
	   }
	else if (source == backButton) {
		if (!(resultField.getText().equals("0") || resultField.getText().equals("0.0")) && resultField.getText().length() > 1){
			resultField.setText(resultField.getText().substring(0,resultField.getText().length()-1));
		}
	    }
         } else
             resultField.setText("Invalid operand");
    }

    public void actionPerformed(ActionEvent ae) {

        source = ae.getSource();
        showResult();
    }
   
}