Membuat Kalkulator di Java

Assalamualaikum wr. wb

Masih berhubungan dengan pemrograman java, pada kesempatan kali ini saya akan memposting program kalkulator yang dibuat dengan tampilan GUI supaya lebih tampilannya lebih menarik. Pada program ini hanya dibuat 1 class, yaitu Class Kalkulator, untuk lebih jelasnya langsung saja ke script untuk program tersebut 

package kalkulator;

import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextArea;

public class Kalkulator implements ActionListener {
JFrame frame = new JFrame("Kalkulator");
JPanel panel = new JPanel(new FlowLayout());
JTextArea text = new JTextArea(2, 17);


JButton button1 = new JButton("1");
JButton button2 = new JButton("2");
JButton button3 = new JButton("3");
JButton button4 = new JButton("4");
JButton button5 = new JButton("5");
JButton button6 = new JButton("6");
JButton button7 = new JButton("7");
JButton button8 = new JButton("8");
JButton button9 = new JButton("9");
JButton button0 = new JButton("0");

JButton buttonAdd = new JButton("+");
JButton buttonSub = new JButton("-");
JButton buttonMultiply = new JButton("*");
JButton buttonDivide = new JButton("/");
JButton buttonEqual = new JButton("=");
JButton buttonClear = new JButton("C");

int number1, number2, result;
int addc = 0, subc = 0, multic = 0, divc = 0;

public void Design() {
frame.setVisible(true);
   frame.setBounds(300, 300, 220, 300);
   frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(panel);
        panel.add(text);
        panel.add(button7);
        panel.add(button8);
        panel.add(button9);
        panel.add(buttonMultiply);
        panel.add(button4);
        panel.add(button5);
   panel.add(button6);
   panel.add(buttonSub);
   panel.add(button1);
   panel.add(button2);
   panel.add(button3);
   panel.add(buttonAdd);
   panel.add(buttonClear);
   panel.add(button0);
   panel.add(buttonDivide);
   panel.add(buttonEqual);

   button1.addActionListener(this);
   button2.addActionListener(this);
   button3.addActionListener(this);
   button4.addActionListener(this);
   button5.addActionListener(this);
   button6.addActionListener(this);
   button7.addActionListener(this);
   button8.addActionListener(this);
   button9.addActionListener(this);
   button0.addActionListener(this);
   buttonAdd.addActionListener(this);
   buttonSub.addActionListener(this);
   buttonMultiply.addActionListener(this);
   buttonDivide.addActionListener(this);
   buttonEqual.addActionListener(this);
   buttonClear.addActionListener(this);
}

public void actionPerformed(ActionEvent e) {
Object source = e.getSource();
   if (source == buttonClear) {
    number1 = 0;
    number2 = 0;
    text.setText("");
   }

   if (source == button1) {
    text.append("1");
   }
   if (source == button2) {
       text.append("2");
   }
   if (source == button3) {
       text.append("3");
   }
   if (source == button4) {
       text.append("4");
   }
   if (source == button5) {
       text.append("5");
   }
   if (source == button6) {
       text.append("6");
   }
   if (source == button7) {
       text.append("7");
   }
   if (source == button8) {
       text.append("8");
   }
   if (source == button9) {
       text.append("9");
   }
   if (source == button0) {
    text.append("0");
   }
   if (source == buttonAdd) {
       number1 = numberReader();
       text.setText("");
       addc = 1;
       subc = 0;
       multic = 0;
       divc = 0;
   }
   if (source == buttonSub) {
       number1 = numberReader();
       text.setText("");
       addc = 0;
       subc = 1;
       multic = 0;
       divc = 0;
   }
   if (source == buttonMultiply) {
    number1 = numberReader();
    text.setText("");
    addc = 0;
    subc = 0;
    multic = 1;
    divc = 0;
   }
   if (source == buttonDivide) {
    number1 = numberReader();
    text.setText("");
    addc = 0;
    subc = 0;
    multic = 0;
    divc = 1;
   }
   if (source == buttonEqual) {
    number2 = numberReader();
    if (addc > 0) {
    result = number1 + number2;
    text.setText(Double.toString(result));
    }
    if (subc > 0) {
    result = number1 - number2;
    text.setText(Double.toString(result));
    }
    if (multic > 0) {
    result = number1 * number2;
    text.setText(Double.toString(result));
    }
    if (divc > 0) {
    result = number1 / number2;
    text.setText(Double.toString(result));
    }
   }

}

public int numberReader() {
int number1;
String s;
s = text.getText();
number1 = Integer.parseInt(s);

return number1;
}

public static void main(String[] args) {
Kalkulator kalkulator = new Kalkulator();
        kalkulator.Design();
}
}

Dan untuk hasilnya setelah program tersebut dijalankan (run) adalah :

Sekian dari saya, semoga bermanfaat.

Wassalamu'alaikum wr.wb