Calculator Application Using Java

Calculator Application Using Java AWT

Here is the java code for a simple calculator application that will look like this.

Code:

import java.awt.*;
import java.awt.event.*;

public class CalGUI implements ActionListener, KeyListener {

    String[] s =  {"", "7", "8", "9", "/", "4", "5", "6", "*", "1", "2", "3", "-", "0", "=", "+", "C"};
    Frame f;
    Button[] b = new Button[16];
    TextField text;
    int x = 35, y = 100;
    float res = 0.0f;   
    String msg = "";
    char op;

    public CalGUI() {
        f = new Frame("Calculator");
        f.setSize(400, 450);
        f.setResizable(false);
        f.setLayout(null);
        f.setBackground(Color.gray);
        text = new TextField(45);
        text.setFocusable(false);
        text.setBounds(25, 40, 350, 40);
        text.setEditable(false);
        text.setFont(new Font("Consolas",1,20));
        f.add(text);
        for (int i = 1; i < s.length; i++) {
            b[i-1] = new Button(s[i]);
            b[i-1].setFont(new Font("Consolas",1,20));
            b[i-1].setBackground(Color.LIGHT_GRAY);
            b[i-1].setBounds(x, y, 80, 80);
            x=x+80;
            if(i % 4 == 0 && i != 0) {y = y + 80; x = 35;}
            f.add(b[i-1]);
        }
        
        f.setVisible(true);
        f.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                System.exit(0);
            }
        });
        
        for(int i = 0; i < b.length; i++) {
            b[i].addActionListener(this);
        }
        f.addKeyListener(this);
        
    }
    
    public void keyPressed(KeyEvent ke)
    {
        char ch = ke.getKeyChar();
        if (ch >= '0' && ch <= '9') {
            msg += ch;
            text.setText(msg);
        }
        else if(ch == '=') {
            switch(op) {
                case '+': 
                    res = res + Integer.parseInt(text.getText()); 
                    break;
                case '-':
                    res = res - Integer.parseInt(text.getText()); 
                    break;
                case '*':
                    res = res * Integer.parseInt(text.getText()); 
                    break;
                case '/':
                    res = res / (float)Integer.parseInt(text.getText()); 
                    break;
                    
            }
            text.setText("Ans. " + res);
            msg="";
        }
        else if(ch == 'C') {
            text.setText("");
            res = 0;
            msg ="";
        }
        else {
            res = Integer.parseInt(text.getText());
            text.setText("");
            msg = "";
            switch(ch) {
                case '+': op = '+'; break;
                case '*': op = '*'; break;
                case '/': op = '/'; break;
                case '-': op = '-'; break;
            }
        }
        
    }
    
    public void actionPerformed(ActionEvent e) {
        String str = e.getActionCommand();
        char ch = str.charAt(0);
        if (ch >= '0' && ch <= '9') {
            msg += str;
            text.setText(msg);
        }
        else if(ch == '=') {
            switch(op) {
                case '+': 
                    res = res + Integer.parseInt(text.getText()); 
                    break;
                case '-':
                    res = res - Integer.parseInt(text.getText()); 
                    break;
                case '*':
                    res = res * Integer.parseInt(text.getText()); 
                    break;
                case '/':
                    res = res / (float)Integer.parseInt(text.getText()); 
                    break;
                    
            }
            text.setText("Ans. " + res);
            msg="";
        }
        else if(ch == 'C') {
            text.setText("");
            res = 0;
            msg ="";
        }
        else {
            res = Integer.parseInt(text.getText());
            text.setText("");
            msg = "";
            switch(ch) {
                case '+': op = '+'; break;
                case '*': op = '*'; break;
                case '/': op = '/'; break;
                case '-': op = '-'; break;
            }
        }
    }
    
    public static void main(String[] arg) {
        new CalGUI();
    }

    @Override
    public void keyTyped(KeyEvent arg0) {
        char ch = arg0.getKeyChar();
        if (ch >= '0' && ch <= '9') {
            msg += ch;
            text.setText(msg);
        }
        else if(ch == '=') {
            switch(op) {
                case '+': 
                    res = res + Integer.parseInt(text.getText()); 
                    break;
                case '-':
                    res = res - Integer.parseInt(text.getText()); 
                    break;
                case '*':
                    res = res * Integer.parseInt(text.getText()); 
                    break;
                case '/':
                    res = res / (float)Integer.parseInt(text.getText()); 
                    break;
                    
            }
            text.setText("Ans. " + res);
            msg="";
        }
        else if(ch == 'C') {
            text.setText("");
            res = 0;
            msg ="";
        }
        else {
            res = Integer.parseInt(text.getText());
            text.setText("");
            msg = "";
            switch(ch) {
                case '+': op = '+'; break;
                case '*': op = '*'; break;
                case '/': op = '/'; break;
                case '-': op = '-'; break;
            }
        }
        
    }

    @Override
    public void keyReleased(KeyEvent arg0) {}
}