Grafico calcular Circulo Java - Netbeans

Tema: Implementar un Programa que me permita dibujar un cuadro estableciendo las coordenadas x0,y0,x1,y1 Para eso se debe crear 1 Paquete con dos interfazes
1.- Jframe
2.- Jpanel

Pasos:
1.- Creamos 1 Nuevo Proyecto en Java Aplicacion
2.- Creamos un Paquete Java
3.- Creamos una Clase Java
4.- Clic derecho dentro del Paquete crear:
     -Formulario JPanel 
     -Formulario Jframe  


Formulario JPanel: Establece la programación 

Formulario Jframe:  Establece la Estructura Gráfica. 






Clase Java:

package appdibujarcirculocalculararea;

public class Calculos 

{

    private int Xo,Yo;

    private int X1,Y1;

    

    public Calculos(int Xo, int Yo, int X1, int Y1)

    {

        this.Xo = Xo;

        this.Yo = Yo;

        this.X1 = X1;

        this.Y1 = Y1;

    }

    private double DistanciaPuntos()

    {

        double d = Math.sqrt((Math.pow((this.X1 - this.Xo), 2)) + (Math.pow((this.Y1 - this.Yo), 2)));

        return d;

    }

    public double AreaCirculo()

    {

       double distancia = this.DistanciaPuntos();

       double radio = distancia / 2;

       double area = Math.PI * Math.pow(radio, 2);

       return area;

    }

    }

JPanel :

package appdibujarcirculocalculararea;


import java.awt.Graphics;
import java.awt.*;




public class Panel extends javax.swing.JPanel {


    private int Xo,Yo;
    private int X1,Y1;


    public void setX1(int X1) {
        this.X1 = X1;
    }


    public void setXo(int Xo) {
        this.Xo = Xo;
    }


    public void setY1(int Y1) {
        this.Y1 = Y1;
    }


    public void setYo(int Yo) {
        this.Yo = Yo;
    }
    public Panel() {
        initComponents();
    }


    @SuppressWarnings("unchecked")
    //                          
    private void initComponents() {


        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(this);
        this.setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 400, Short.MAX_VALUE)
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 300, Short.MAX_VALUE)
        );
    }//                        
    @Override
    public void paint(Graphics g) {
        super.paint(g);
        g.setColor(Color.red);
        g.drawOval(this.Xo, this.Yo, this.X1, this.Y1);
        
        Calculos Obj = new Calculos(this.Xo, this.Yo, this.X1, this.Y1);
        double a = Obj.AreaCirculo();
        String cadena = "Area = " + String.valueOf(a);
        g.drawString(cadena, 10, 15);
    }
    public void DibujarCirculo()
    {
      repaint();
    }
    // Variables declaration - do not modify                     
    // End of variables declaration                   
} 




JFrame :

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */


/*
 * Principal.java
 *
 * Created on 26/08/2011, 08:04:16 AM
 */


package appdibujarcirculocalculararea;


/**
 *
 * @author lab.sistemas
 */
public class Principal extends javax.swing.JFrame {


    /** Creates new form Principal */
    public Principal() {
        initComponents();
    }


    /** This method is called from within the constructor to
     * initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is
     * always regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    //                          
    private void initComponents() {


        jPanel1 = new javax.swing.JPanel();
        jLabel1 = new javax.swing.JLabel();
        textX0 = new javax.swing.JTextField();
        jLabel2 = new javax.swing.JLabel();
        jLabel3 = new javax.swing.JLabel();
        jLabel4 = new javax.swing.JLabel();
        texty0 = new javax.swing.JTextField();
        textX1 = new javax.swing.JTextField();
        texty1 = new javax.swing.JTextField();
        btngraficar = new javax.swing.JButton();
        jLabel6 = new javax.swing.JLabel();
        jLabel5 = new javax.swing.JLabel();
        panel1 = new appdibujarcirculocalculararea.Panel();


        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setBackground(new java.awt.Color(102, 102, 255));
        setCursor(new java.awt.Cursor(java.awt.Cursor.DEFAULT_CURSOR));
        setForeground(java.awt.Color.white);


        jPanel1.setBackground(new java.awt.Color(0, 153, 153));
        jPanel1.setBorder(new javax.swing.border.SoftBevelBorder(javax.swing.border.BevelBorder.RAISED));


        jLabel1.setFont(new java.awt.Font("Tahoma", 1, 11));
        jLabel1.setForeground(new java.awt.Color(255, 255, 255));
        jLabel1.setText("X0:");


        jLabel2.setFont(new java.awt.Font("Tahoma", 1, 11));
        jLabel2.setForeground(new java.awt.Color(255, 255, 255));
        jLabel2.setText("Y0:");


        jLabel3.setFont(new java.awt.Font("Tahoma", 1, 11));
        jLabel3.setForeground(new java.awt.Color(255, 255, 255));
        jLabel3.setText("x1:");


        jLabel4.setFont(new java.awt.Font("Tahoma", 1, 11));
        jLabel4.setForeground(new java.awt.Color(255, 255, 255));
        jLabel4.setText("y1");


        btngraficar.setText("Graficar");
        btngraficar.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btngraficarActionPerformed(evt);
            }
        });


        jLabel6.setFont(new java.awt.Font("Tahoma", 1, 11));
        jLabel6.setForeground(new java.awt.Color(255, 255, 255));
        jLabel6.setText("Zona Java 2011");


        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(jPanel1Layout.createSequentialGroup()
                        .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                            .addGroup(jPanel1Layout.createSequentialGroup()
                                .addComponent(jLabel1)
                                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                .addComponent(textX0, javax.swing.GroupLayout.PREFERRED_SIZE, 38, javax.swing.GroupLayout.PREFERRED_SIZE)
                                .addGap(69, 69, 69)
                                .addComponent(jLabel3))
                            .addGroup(jPanel1Layout.createSequentialGroup()
                                .addComponent(jLabel2)
                                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                .addComponent(texty0, javax.swing.GroupLayout.PREFERRED_SIZE, 38, javax.swing.GroupLayout.PREFERRED_SIZE)
                                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                                .addComponent(jLabel4)))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addComponent(textX1, javax.swing.GroupLayout.PREFERRED_SIZE, 38, javax.swing.GroupLayout.PREFERRED_SIZE)
                            .addComponent(texty1, javax.swing.GroupLayout.PREFERRED_SIZE, 38, javax.swing.GroupLayout.PREFERRED_SIZE))
                        .addGap(36, 36, 36)
                        .addComponent(btngraficar)
                        .addContainerGap())
                    .addComponent(jLabel6, javax.swing.GroupLayout.Alignment.TRAILING)))
        );
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addGap(49, 49, 49)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel1)
                    .addComponent(textX0, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jLabel3)
                    .addComponent(textX1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel2)
                    .addComponent(jLabel4)
                    .addComponent(texty0, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(texty1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel1Layout.createSequentialGroup()
                .addContainerGap(59, Short.MAX_VALUE)
                .addComponent(btngraficar)
                .addGap(15, 15, 15)
                .addComponent(jLabel6))
        );


        jLabel5.setFont(new java.awt.Font("Vineta BT", 0, 18));
        jLabel5.setText("CIRCULO CALCULO DE AREA ");


        javax.swing.GroupLayout panel1Layout = new javax.swing.GroupLayout(panel1);
        panel1.setLayout(panel1Layout);
        panel1Layout.setHorizontalGroup(
            panel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 387, Short.MAX_VALUE)
        );
        panel1Layout.setVerticalGroup(
            panel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 133, Short.MAX_VALUE)
        );


        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addComponent(jPanel1, javax.swing.GroupLayout.Alignment.TRAILING, javax.swing.GroupLayout.DEFAULT_SIZE, 428, Short.MAX_VALUE)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jLabel5)
                .addContainerGap(162, Short.MAX_VALUE))
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(panel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(31, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                .addComponent(jLabel5, javax.swing.GroupLayout.PREFERRED_SIZE, 25, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addComponent(panel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addGap(18, 18, 18)
                .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
        );


        pack();
    }//                        


    private void btngraficarActionPerformed(java.awt.event.ActionEvent evt) {                                            
       int Xo = Integer.parseInt(this.textX0.getText());
       int Yo = Integer.parseInt(this.texty0.getText());
       int X1 = Integer.parseInt(this.textX1.getText());
       int Y1 = Integer.parseInt(this.texty1.getText());


       panel1.setXo(Xo);
       panel1.setYo(Yo);
       panel1.setX1(X1);
       panel1.setY1(Y1);


       panel1.DibujarCirculo();


    }                                           


    /**
    * @param args the command line arguments
    */
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new Principal().setVisible(true);
            }
        });
    }


    // Variables declaration - do not modify                     
    private javax.swing.JButton btngraficar;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JLabel jLabel4;
    private javax.swing.JLabel jLabel5;
    private javax.swing.JLabel jLabel6;
    private javax.swing.JPanel jPanel1;
    private appdibujarcirculocalculararea.Panel panel1;
    private javax.swing.JTextField textX0;
    private javax.swing.JTextField textX1;
    private javax.swing.JTextField texty0;
    private javax.swing.JTextField texty1;
    // End of variables declaration                   


}



Ejecución: