Java Swing | Simple Calculator

Java Swing is a GUI (graphical user Interface) widget toolkit for Java. Java Swing is a part of Oracle’s Java foundation classes . Java Swing is an API for providing graphical user interface elements to Java Programs.Swing was created to provide more powerful and flexible components than Java AWT (Abstract Window Toolkit).

In this article we will use Java Swing components to create a simple calculator with only +, -, /, * operations.



methods used :

  1. add(Component c) : adds component to container.
  2. addActionListenerListener(ActionListener d) : add actionListener for specified component
  3. setBackground(Color c) : sets the background color of the specified container
  4. setSize(int a, int b) : sets the size of container to specified dimensions.
  5. setText(String s) : sets the text of the label to s.
  6. getText() : returns the text of the label.

Java program to create a simple calculator with basic +, -, /, * using java swing elements.

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// Java program to create a simple calculator
// with basic +, -, /, * using java swing elements
  
import java.awt.event.*;
import javax.swing.*;
import java.awt.*;
class calculator extends JFrame implements ActionListener {
    // create a frame
    static JFrame f;
  
    // create a textfield
    static JTextField l;
  
    // store oprerator and operands
    String s0, s1, s2;
  
    // default constrcutor
    calculator()
    {
        s0 = s1 = s2 = "";
    }
  
    // main function
    public static void main(String args[])
    {
        // create a frame
        f = new JFrame("calculator");
  
        try {
            // set look and feel
            UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
        }
        catch (Exception e) {
            System.err.println(e.getMessage());
        }
  
        // create a object of class
        calculator c = new calculator();
  
        // create a textfield
        l = new JTextField(16);
  
        // set the textfield to non editable
        l.setEditable(false);
  
        // create number buttons and some operators
        JButton b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, ba, bs, bd, bm, be, beq, beq1;
  
        // create number buttons
        b0 = new JButton("0");
        b1 = new JButton("1");
        b2 = new JButton("2");
        b3 = new JButton("3");
        b4 = new JButton("4");
        b5 = new JButton("5");
        b6 = new JButton("6");
        b7 = new JButton("7");
        b8 = new JButton("8");
        b9 = new JButton("9");
  
        // equals button
        beq1 = new JButton("=");
  
        // create operator buttons
        ba = new JButton("+");
        bs = new JButton("-");
        bd = new JButton("/");
        bm = new JButton("*");
        beq = new JButton("C");
  
        // create . button
        be = new JButton(".");
  
        // create a panel
        JPanel p = new JPanel();
  
        // add action listeners
        bm.addActionListener(c);
        bd.addActionListener(c);
        bs.addActionListener(c);
        ba.addActionListener(c);
        b9.addActionListener(c);
        b8.addActionListener(c);
        b7.addActionListener(c);
        b6.addActionListener(c);
        b5.addActionListener(c);
        b4.addActionListener(c);
        b3.addActionListener(c);
        b2.addActionListener(c);
        b1.addActionListener(c);
        b0.addActionListener(c);
        be.addActionListener(c);
        beq.addActionListener(c);
        beq1.addActionListener(c);
  
        // add elements to panel
        p.add(l);
        p.add(ba);
        p.add(b1);
        p.add(b2);
        p.add(b3);
        p.add(bs);
        p.add(b4);
        p.add(b5);
        p.add(b6);
        p.add(bm);
        p.add(b7);
        p.add(b8);
        p.add(b9);
        p.add(bd);
        p.add(be);
        p.add(b0);
        p.add(beq);
        p.add(beq1);
  
        // set Background of panel
        p.setBackground(Color.blue);
  
        // add panel to frame
        f.add(p);
  
        f.setSize(200, 220);
        f.show();
    }
    public void actionPerformed(ActionEvent e)
    {
        String s = e.getActionCommand();
  
        // if the value is a number
        if ((s.charAt(0) >= '0' && s.charAt(0) <= '9') || s.charAt(0) == '.') {
            // if operand is present then add to second no
            if (!s1.equals(""))
                s2 = s2 + s;
            else
                s0 = s0 + s;
  
            // set the value of text
            l.setText(s0 + s1 + s2);
        }
        else if (s.charAt(0) == 'C') {
            // clear the one letter
            s0 = s1 = s2 = "";
  
            // set the value of text
            l.setText(s0 + s1 + s2);
        }
        else if (s.charAt(0) == '=') {
  
            double te;
  
            // store the value in 1st
            if (s1.equals("+"))
                te = (Double.parseDouble(s0) + Double.parseDouble(s2));
            else if (s1.equals("-"))
                te = (Double.parseDouble(s0) - Double.parseDouble(s2));
            else if (s1.equals("/"))
                te = (Double.parseDouble(s0) / Double.parseDouble(s2));
            else
                te = (Double.parseDouble(s0) * Double.parseDouble(s2));
  
            // set the value of text
            l.setText(s0 + s1 + s2 + "=" + te);
  
            // convert it to string
            s0 = Double.toString(te);
  
            s1 = s2 = "";
        }
        else {
            // if there was no operand
            if (s1.equals("") || s2.equals(""))
                s1 = s;
            // else evaluate
            else {
                double te;
  
                // store the value in 1st
                if (s1.equals("+"))
                    te = (Double.parseDouble(s0) + Double.parseDouble(s2));
                else if (s1.equals("-"))
                    te = (Double.parseDouble(s0) - Double.parseDouble(s2));
                else if (s1.equals("/"))
                    te = (Double.parseDouble(s0) / Double.parseDouble(s2));
                else
                    te = (Double.parseDouble(s0) * Double.parseDouble(s2));
  
                // convert it to string
                s0 = Double.toString(te);
  
                // place the operator
                s1 = s;
  
                // make the operand blank
                s2 = "";
            }
  
            // set the value of text
            l.setText(s0 + s1 + s2);
        }
    }
}

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Output :


Note : this program might not run in an online compiler please use an offline IDE.



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Second year Department of Information Technology Jadavpur University

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