JAVA Assignment LAB

import javax.swing.*;
import java.awt.event.*;


class Calc implements ActionListener
{
    JFrame f;
    JTextField t;
    JButton b1,b2,b3,b4,b5,b6,b7,b8,b9,b0,bdiv,bmul,bsub,badd,beq,bclr;

    public int a=0,b=0,result=0;
    public int operator=0;

    Calc()
    {
        f=new JFrame("Calculator");
        t=new JTextField();
        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");
        b0=new JButton("0");
        bdiv=new JButton("/");
        bmul=new JButton("*");
        bsub=new JButton("-");
        badd=new JButton("+");

        beq=new JButton("=");
        bclr=new JButton("Clear");

        t.setBounds(20,40,200,30);     // X axis, y axis, Height, WIdth

        b1.setBounds(30,240,50,40);
        b2.setBounds(95,240,50,40);
        b3.setBounds(160,240,50,40);
        b4.setBounds(30,170,50,40);
        b5.setBounds(95,170,50,40);
        b6.setBounds(160,170,50,40);
        b7.setBounds(30,100,50,40);
        b8.setBounds(95,100,50,40);
        b9.setBounds(160,100,50,40);
        b0.setBounds(100,300,50,40);

        badd.setBounds(250,120,50,40);
        bdiv.setBounds(250,200,50,40);          //

        bsub.setBounds(250,160,50,40);    //
        bmul.setBounds(250,240,50,40);
        bclr.setBounds(20,350,100,40);                   //
        beq.setBounds(120,350,100,40);

        f.add(t);

        f.add(bdiv);
        f.add(b1);
        f.add(b2);
        f.add(b3);
        f.add(b4);
        f.add(b5);
        f.add(b6);
        f.add(b7);
        f.add(b8);
        f.add(b9);
        f.add(b0);
        f.add(bmul);
        f.add(bsub);
        f.add(beq);
        f.add(badd);
        f.add(bclr);




        f.setLayout(null);
        f.setVisible(true);
        f.setSize(320,450);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setResizable(false);

        b1.addActionListener(this);
        b2.addActionListener(this);
        b3.addActionListener(this);
        b4.addActionListener(this);
        b5.addActionListener(this);
        b6.addActionListener(this);
        b7.addActionListener(this);
        b8.addActionListener(this);
        b9.addActionListener(this);
        b0.addActionListener(this);
        badd.addActionListener(this);
        bdiv.addActionListener(this);
        bmul.addActionListener(this);
        bsub.addActionListener(this);

        beq.addActionListener(this);

        bclr.addActionListener(this);
    }

    public void actionPerformed(ActionEvent e)
    {
        if(e.getSource()==b1)
            t.setText(t.getText().concat("1"));

        if(e.getSource()==b2)
            t.setText(t.getText().concat("2"));

        if(e.getSource()==b3)
            t.setText(t.getText().concat("3"));

        if(e.getSource()==b4)
            t.setText(t.getText().concat("4"));

        if(e.getSource()==b5)
            t.setText(t.getText().concat("5"));

        if(e.getSource()==b6)
            t.setText(t.getText().concat("6"));

        if(e.getSource()==b7)
            t.setText(t.getText().concat("7"));

        if(e.getSource()==b8)
            t.setText(t.getText().concat("8"));

        if(e.getSource()==b9)
            t.setText(t.getText().concat("9"));

        if(e.getSource()==b0)
            t.setText(t.getText().concat("0"));


        if(e.getSource()==badd)
        {
            a=Integer.parseInt(t.getText());
            operator=1;
            t.setText("");
        }

        if(e.getSource()==bsub)
        {
            a=Integer.parseInt(t.getText());
            operator=2;
            t.setText("");
        }

        if(e.getSource()==bmul)
        {
            a=Integer.parseInt(t.getText());
            operator=3;
            t.setText("");
        }

        if(e.getSource()==bdiv)
        {
            a=Integer.parseInt(t.getText());
            operator=4;
            t.setText("");
        }

        if(e.getSource()==beq)
        {
            b=Integer.parseInt(t.getText());

            switch(operator)
            {
                case 1: result=a+b;
                    break;

                case 2: result=a-b;
                    break;

                case 3: result=a*b;
                    break;

                case 4: result=a/b;
                    break;

                default: result=0;
            }

            t.setText(""+result);
        }

        if(e.getSource()==bclr)
            t.setText("");


    }

    public static void main(String []args)
    {
        new Calc();
    }
}