BlueJ (area of circle)

A simple program to calculate the area of a circle. radius provided by user.

this is what i got but i can't compile it without an error. please help if you identify my mistake.

public class stage1 { // BEGIN Area of Circle

/**
 *    Get radius from user
 *    Set area = Math.Pi * radius * radius
 *    Output "Area : " area
 * END Area of Circle
 */

public static void main(String [] areaCircle) 
{
    Scanner keyboard = new Scanner(System.in);
    System.out.println("Enterh the circle's radius: ");
    double radius = keyboard.nextDouble();
    System.out.println("int Area");
}

}

import java.util.Scanner;
public class AreaOfCircle { 

public static void main(String [] str) 
{
    Scanner keyboard = new Scanner(System.in);
    System.out.println("Enter the circle's radius: ");
    double radius = keyboard.nextDouble();
    double PI=3.14;
    double area=PI*radius*radius;
    System.out.println("Area of circle: "+area);
    }
}

import javax.swing.JOptionPane;
public class constant
{
public static void main(String[]args)
{

 final double PI = 3.142;
 double R1,R2,area,average;
 String input;

 input= JOptionPane.showInputDialog("AREA");
 area=Integer.parseInt(input);

 input= JOptionPane.showInputDialog("Radius 1");
 R1=Integer.parseInt(input);

 input= JOptionPane.showInputDialog("Radius 2");
 R2=Integer.parseInt(input);

 average=(area=PI*R1*R2);

 JOptionPane.showMessageDialog(null,"Area of circle: "+ area);
 System.exit(0);