/**
 * 
 */
package hornick;

import java.text.DecimalFormat;

import javax.swing.JOptionPane;

/**
 * @author hornick
 * 10/16/2007
 * Solution to Lab1 volume calculator demonstrated in class, with an additional method added
 */
public class VolumeCalculatorApp {

	/**
	 * main() method is the starting point for all Java applications
	 * @param args
	 */
	public static void main(String[] args) {

		// ask the user for input, and convert the input to a numerical value
		String input;
		double radius;

		int answer=0;
		do {

			input = JOptionPane.showInputDialog("Enter the radius of a sphere");
			if( input==null ) {
				System.exit(0);
			}
			if(  input.length()==0 )   {
				answer = JOptionPane.showConfirmDialog(null, "Want to try again?", "You entered an empty string", JOptionPane.YES_NO_OPTION, JOptionPane.QUESTION_MESSAGE);
			}
		}
		
		while( answer == JOptionPane.YES_OPTION);
		
		if( answer != JOptionPane.YES_OPTION )
			System.exit(0);
		
		radius = Double.parseDouble(input);


//		assuming that the input was a valid set of characters representing a number
		if( radius < 0 ) {	// check for invalid radius
			JOptionPane.showMessageDialog(null, "Error. Radius is <= 0" );
		}
		else {					// radius is valid
			double volume;
			volume = calculateVolume(radius);	// call a method to do the actual computation

			// convert the numerical result to a string with proper formatting
			DecimalFormat sdf;
			sdf = new DecimalFormat("00.000");
			String output = sdf.format(volume); // format the output
			JOptionPane.showMessageDialog(null, "Volume of sphere: " + output + "\nPress OK to exit.", "Result", 2);
		}
	}

	/**
	 * This is a "worker" method that does the actual volume calculation
	 * @param r the radius of the sphere
	 * @return the volume of the sphere
	 */
	public static  double calculateVolume(double r) {
		double v = 4./3  *  Math.PI * r*r*r;  // instead of r*r*r, you can use Math.pow(r,3)
		return v;
	}

}