Java desktop application for computing the roots of a quadratic equation – Source code

The source code of a Java desktop application for solving a quadratic equation is shown below. The application is built using this Java code for computing the roots of the equation.

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.lang.Math;
import java.awt.font.TextAttribute;
import java.text.AttributedString;

public class QuadCalc implements ActionListener{

   JFrame frame;
   MyPanel panel;
   JTextArea textArea;
   JLabel aLabel, bLabel, cLabel;
   JTextField aBox,bBox,cBox;
   JButton[] functionButtons = new JButton[2];
   JButton submitButton, clearButton;
   JPanel labelPane;
	
   Font myFont = new Font("Arial",Font.BOLD,18);
   Font myFont2 = new Font("Arial",Font.PLAIN,14);
   Color myColor = new Color(240,250,255);
	
   double a=0,b=0,c=0,x=0,x1=0,x2=0;
   String prnText = ""; 
   String s;

   QuadCalc(){
	
      frame = new JFrame("Quadratic Equation Solver");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.setSize(420, 550);             
      frame.setLayout(null);
      frame.setLocationRelativeTo(null);
      panel = new MyPanel();	
	
      textArea = new JTextArea();
      textArea.setBounds(50, 300, 300, 100);
      textArea.setFont(myFont2);
      textArea.setEditable(false);
      textArea.setLineWrap(true); 
      textArea.setWrapStyleWord(true); 

      aLabel = new JLabel("a: ",JLabel.RIGHT);
      aLabel.setFont(new Font("Verdana", Font.BOLD, 18));
      aBox = new JTextField();
      aBox.setBounds(100, 150, 50, 50);
      aBox.setBackground(new Color(240,250,255));
      aBox.setFont(myFont);
      aBox.setEditable(true);
      aBox.addActionListener(this);
 
      bLabel = new JLabel("b: ",JLabel.RIGHT);
      bLabel.setFont(new Font("Verdana", Font.BOLD, 18));
      bBox = new JTextField();
      bBox.setBounds(200, 150, 50, 50);
      bBox.setBackground(myColor);
      bBox.setFont(myFont);
      bBox.setEditable(true);
      bBox.addActionListener(this);

      cLabel = new JLabel("c: ",JLabel.RIGHT);
      cLabel.setFont(new Font("Verdana", Font.BOLD, 18));
      cBox = new JTextField();
      cBox.setBounds(300, 150, 50, 50);
      cBox.setBackground(myColor);
      cBox.setFont(myFont);
      cBox.setEditable(true);
      cBox.addActionListener(this);
		
      //Lay out the labels and text boxes in a panel.
      labelPane = new JPanel();
      labelPane.setBounds(50,150,300,50);
      labelPane.setLayout(new GridLayout(1,6));
      labelPane.add(aLabel);
      labelPane.add(aBox);
      labelPane.add(bLabel);
      labelPane.add(bBox);
      labelPane.add(cLabel);
      labelPane.add(cBox);

      submitButton = new JButton("Submit");
      submitButton.setBounds(50,225,100,50);
      clearButton = new JButton("Clear");		
      clearButton.setBounds(50,430,100,50);
      functionButtons[0] = submitButton;
      functionButtons[1] = clearButton;
		
      for(int i =0;i<2;i++) {
         functionButtons[i].addActionListener(this);
         functionButtons[i].setFont(myFont);
         functionButtons[i].setFocusable(false);
      }				
			
      frame.add(submitButton);
      frame.add(clearButton);
      frame.add(labelPane);
      frame.add(textArea); 
      frame.add(panel);
      frame.setVisible(true);

   }
	
   public static void main(String[] args) {		
      QuadCalc calc = new QuadCalc();
   }

   class MyPanel extends JPanel{
 
      MyPanel(){
  
      this.setBounds(25,25,325,150);
      }
 
      public void paint(Graphics g) {
  
         Graphics2D g2D = (Graphics2D) g;

         String prnText1 = "A quadratic equation has a form of";
         String prnText2 = "aX2 + bX + c = 0";
         String prnText3 = "To solve your equation, enter values";
         String prnText4 = "of a, b, c into the boxes:";
         // superscript 
         AttributedString supText = new AttributedString(prnText2);
         supText.addAttribute(TextAttribute.SIZE, 18, 0, 16);
         supText.addAttribute(TextAttribute.SUPERSCRIPT, TextAttribute.SUPERSCRIPT_SUPER, 2, 3);

         g2D.setPaint(Color.BLUE);
         g2D.setFont(new Font("Dialog",Font.PLAIN,18));
         g2D.drawString(prnText1,25,25);
         g2D.drawString(supText.getIterator(), 25, 50);
         g2D.drawString(prnText3,25,75);
         g2D.drawString(prnText4,25,100);
 
     }
   }
	
   @Override
   public void actionPerformed(ActionEvent e) {		
      if(e.getSource()==submitButton) {
	 a=Double.parseDouble(aBox.getText());
	 b=Double.parseDouble(bBox.getText());
	 c=Double.parseDouble(cBox.getText());
    	 if (a == 0.0) {
       	    if (b == 0.0) {
               if (c != 0) {
                  prnText = "The equation has no solutions";
               } else {
                  prnText = "The equation has infinite solutions";
               }
            } else {
          	x = -c/b;
          	s = String.format("%.2f",x);
          	prnText = "The equation is linear and has one root:\nX = ".concat(s);
       	    }
    	 } else {
       	    double delta = b*b - 4*a*c;
       	    if (delta == 0.0) {
          	x = -b/(2*a);
          	s = String.format("%.2f",x);
          	prnText="The equation has one unique root: \nX = ".concat(s);               
       	    } else if (delta > 0.0) {
          	double x1 = (-b - Math.sqrt(delta))/(2*a);
          	double x2 = (-b + Math.sqrt(delta))/(2*a);
          	s = String.format("%.2f",x1);
          	prnText="The equation has two roots: \n"+"X1 = ".concat(s);
          	prnText += ",\n"+ "X2 = "+String.format("%.2f",x2);
       	    } else if (delta < 0.0) {
          	double realx = -b/(2*a);
          	double imx = (Math.sqrt(Math.abs(delta)))/(2*a);
          	prnText="The equation has two conjugate complex roots\n";
		prnText += "X1 = "+String.format("%.2f",realx)+" - i("+String.format("%.2f",Math.abs(imx))+"), \n";
          	prnText += "X2 = "+String.format("%.2f",realx)+" + i("+String.format("%.2f",Math.abs(imx))+")";
       	    }
    	}
	textArea.setText(prnText);
    }
    if(e.getSource()==clearButton) {
	textArea.setText("");
	aBox.setText("");
	bBox.setText("");
	cBox.setText("");
    }
  }
}