Java GUI code- creating a circle

My assignment is to write a program that prompts the user to enter the center and a point on the circle, which is (x,y)(x2,y2). The program should then output the circle's radius, circumference, and area. I did my code but I can't seem to figure out the mathematical code, can someone please help me?

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

    public class CircleGUI extends JFrame {
        //variables
        double clx = 0.0, cly = 0.0, circumrx = 0.0, circumry = 0.0; //top-left and bottom-right coordinates
        ButtonHandler buttonHandler;

        //GUI components
        JLabel lClx, lCly, lCircumrx, lCircumry, lRadius, lArea, lCircumference;
        JTextField tClx, tCly, tCircumrx, tCircumry, tRadius, tArea, tCircumference;
        JButton bReset, bCompute;
        Container c;
        JPanel pNorth, pWest, pCenter, pSouth;

        //methods

        //constructor
        public CircleGUI() {
            //create GUI
            lClx = new JLabel("Center X");
            lCly = new JLabel("Center Y");
            lCircumrx = new JLabel("Circumference X");
            lCircumry = new JLabel("Circumference Y");
            lRadius = new JLabel("Radius");
            lArea = new JLabel("Area");
            lCircumference = new JLabel("Circumference");
            tClx = new JTextField();
            tCly = new JTextField();
            tCircumrx = new JTextField();
            tCircumry = new JTextField();
            tRadius = new JTextField();
            tArea = new JTextField();
            tCircumference= new JTextField();
            bReset = new JButton("Reset");
            bCompute = new JButton("Compute");
            pNorth = new JPanel();
            pWest = new JPanel();
            pCenter = new JPanel();
            pSouth = new JPanel();
            c = getContentPane();

            //add components
            c.setLayout(new BorderLayout());
            pNorth.setLayout(new GridLayout(2,4));
            pWest.setLayout(new GridLayout(4,2));
            pCenter.setLayout(new GridLayout(4,2));
            pSouth.setLayout(new GridLayout(1,2));

            c.add(pNorth, BorderLayout.NORTH);
            c.add(pWest, BorderLayout.WEST);
            c.add(pCenter, BorderLayout.CENTER);
            c.add(pSouth, BorderLayout.SOUTH);

            pNorth.add(lClx);
            pNorth.add(tClx);
            pNorth.add(lCly);
            pNorth.add(tCly);
            pNorth.add(lCircumrx);
            pNorth.add(tCircumrx);
            pNorth.add(lCircumry);
            pNorth.add(tCircumry);
            pWest.add(lRadius);
            pWest.add(lArea);
            pWest.add(lCircumference);
            pCenter.add(tRadius);
            pCenter.add(tArea);
            pCenter.add(tCircumference);
            pSouth.add(bReset);
            pSouth.add(bCompute);

            //register with buttons
            buttonHandler = new ButtonHandler();
            bReset.addActionListener(buttonHandler);
            bCompute.addActionListener(buttonHandler);

            //render the window
            setSize(400, 200);
            setLocation(100, 100);
            setResizable(false);
            setTitle("Circle GUI");
            setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            setVisible(true);

        }

        //button handler class
        private class ButtonHandler implements ActionListener {
            public void actionPerformed(ActionEvent ae) {
                if (ae.getSource().equals(bCompute)) {
                    try {
                        clx = Double.parseDouble(tClx.getText());
                        cly = Double.parseDouble(tCly.getText());
                        circumrx = Double.parseDouble(tCircumrx.getText());
                        circumry = Double.parseDouble(tCircumry.getText());
                        Circle obj = new Circle(clx, cly, circumrx, circumry);
                        tRadius.setText(obj.getLength()+"");
                        tArea.setText(obj.getArea()+"");
                        tCircumference.setText(obj.getCircumference()+"");
                    }
                    catch (Exception e) {
                        JOptionPane.showMessageDialog(null, "Fix your input");
                        return;
                    }
                }
                else {
                    tClx.setText("");
                    tCly.setText("");
                    tCircumrx.setText("");
                    tCircumry.setText("");
                    tRadius.setText("");
                    tArea.setText("");
                    tCircumference.setText("");

                }
            }

        }

        /**
         * @param args
         */
        public static void main(String[] args) {
            // TODO Auto-generated method stub
            CircleGUI newApp = new CircleGUI();

        }

    }