Java Calculator

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

public class calculator extends JFrame implements ActionListener{
	
	static JFrame f;
	static JTextField l;
	
	String s0,s1,s2;
	
	calculator(){
		s0 = s1 = s2 = "";
	}
	
	public static void main(String[] args) {
		
		f = new JFrame("calculator");
		
		try {
			UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
		}
		catch(Exception e) {
			System.err.println(e.getMessage());
		}
		
		calculator c = new calculator();
		
		l = new JTextField(16);
		
		l.setEditable(false);
		
		JButton b0,b1,b2,b3,b4,b5,b6,b7,b8,b9,ba,bs,bd,bm,be,beq,beq1;
		
		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");
		
		beq1 = new JButton("=");
		
		ba = new JButton("+");
		bs = new JButton("-");
		bd = new JButton("/");
		bm = new JButton("*");
		beq = new JButton("C");
		
		be = new JButton(".");
		
		JPanel p = new JPanel();
		
		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);
		
		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);
		
		p.setBackground(Color.BLUE);
		
		f.add(p);
		f.setSize(200,220);
		f.show();

	}

	@Override
	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') {
	        	s0 = s1 = s2 = "";
	        	l.setText(s0+s1+s2);
	        	
			} else if(s.charAt(0) == '=') {
				
				double te = 0;
				
				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 if(s1.equals("*"))
					te = (Double.parseDouble(s0) * Double.parseDouble(s2));
				
				l.setText(s0 + s1 + s2 + "=" + te);
				
				s0 = Double.toString(te);
				
				s1 = s2 = "";
				
			} else {
				if(s1.equals("") || s2.equals(""))
					s1 = s;
				else {
					double te;
					
					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));
					
					s0 = Double.toString(te);
					
					s1 = s;
					
					s2 = "";
				}
				
				l.setText(s0+s1+s2);
			}
		}	
	}