Калькулятор ax2+bx+c - Java

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
 
public class Main extends JFrame {
 
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                Main window = new Main("Calculator");
                window.f1.setVisible(true);
            }
        });
    }
 
    JButton b1, b2;
    JTextField t1, t2, t3;
    JLabel l1;
    JFrame f1;
    double a, b, c, d, x1, x2;
    String s1, s2, s3;
    eHandler handler = new eHandler();  
 
    public Main(String s) {
        super(s);
        
        f1 = new JFrame();
        f1.setBounds(100, 100, 300, 200);
        f1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f1.getContentPane().setLayout(null);
        
        b1 = new JButton("Solve");
        b1.setBounds(0, 61, 284, 50);
        f1.getContentPane().add(b1);
        
        t1 = new JTextField();
        t1.setColumns(10);
        t1.setBounds(0, 39, 94, 20);
        f1.getContentPane().add(t1);
        
        b2 = new JButton("Clear");
        b2.setBounds(0, 112, 284, 50);
        f1.getContentPane().add(b2);
        
        t2 = new JTextField();
        t2.setColumns(10);
        t2.setBounds(96, 39, 94, 20);
        f1.getContentPane().add(t2);
        
        t3 = new JTextField();
        t3.setColumns(10);
        t3.setBounds(192, 39, 94, 20);
        f1.getContentPane().add(t3);
        
        JLabel l1 = new JLabel();
        l1.setBounds(3, 0, 281, 39);
        f1.getContentPane().add(l1);
        
        b1.addActionListener(handler);
        b2.addActionListener(handler);
 
    }
 
    public class eHandler implements ActionListener {
        public void actionPerformed(ActionEvent e) {
 
            if (e.getSource() == b1) {
                a = Double.parseDouble(t1.getText());
                b = Double.parseDouble(t2.getText());
                c = Double.parseDouble(t3.getText());
                
                d = (b*b) - (4*a*c);
                x1 = ((-b + Math.sqrt(d))/(2*a));
                x2 = ((-b - Math.sqrt(d))/(2*a));
                
                s1 = "x1 = " + x1;
                s2 = "x2 = " + x2;
                s3 = s1 + " " + s2;
 
                l1.setText(s3);
            }
 
            if (e.getSource() == b2) {
                t1.setText(null);
                t2.setText(null);
                t3.setText(null);
                l1.setText(null);
            }
 
        }
 
    }
}