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 :
- add(Component c) : adds component to container.
- addActionListenerListener(ActionListener d) : add actionListener for specified component
- setBackground(Color c) : sets the background color of the specified container
- setSize(int a, int b) : sets the size of container to specified dimensions.
- setText(String s) : sets the text of the label to s.
- getText() : returns the text of the label.
Java program to create a simple calculator with basic +, -, /, * using java swing elements.
// 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 operator and operands
String s0, s1, s2;
// default constructor
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);
}
}
} |
Output :
Note : this program might not run in an online compiler please use an offline IDE.