import java.math.BigInteger;

/**
 * Natural Number
 * Implementation of a natural number using BigInteger
 * Definition of a natural number can be found in Natural.isNatural(BigInteger n)
 * 
 * Use this code freely, but be sure to leave this comment in the code :)
 * 
 * @author Doug Swain (doug@theswain.net)
 * http://www.theswain.net
 */
@SuppressWarnings("serial")
public class Natural extends BigInteger {
	/**
	 * Constructor to create a Natural from an array of bytes
	 * 
	 * @param naturalNumber The value of the natural number
	 * @throws NumberFormatException If the number is not a natural number
	 */
	public Natural(byte[] naturalNumber) throws NumberFormatException {
		super(naturalNumber);

		if (!isNatural(this))
			throw new NumberFormatException("The number n must be a natural number - " + naturalNumber + " >= 0");
	}

	/**
	 * Constructor to create a Natural from an array of bytes
	 * 
	 * @param naturalNumber The value of the natural number
	 * @throws NumberFormatException If the number is not a natural number
	 */
	public Natural(String naturalNumber) throws NumberFormatException {
		super(naturalNumber);

		if (!isNatural(this))
			throw new NumberFormatException("The number n must be a natural number - " + naturalNumber + " >= 0");
	}
	
	/**
	 * Defines whether a number (n) is natural or not
	 * 
	 * @param BigInteger n The number to verify is natural
	 * @return boolean Whether or not n is natural or not
	 */
	public static boolean isNatural(BigInteger n) {
		return n.compareTo(BigInteger.ZERO) >= 0;
	}

	/**
	 * Main method used for simple unit testing
	 */
	public static void main(String[] args) {
		Natural n = null;
		
		try {
			n = new Natural("7598732975932646".getBytes());
			System.out.println("Natural: " + n);
			
			n = new Natural("563476592396");
			System.out.println("Natural: " + n);
		} catch (NumberFormatException nfe) {
			System.out.println("Failed: " + nfe);
		}
		
		Exception nfe = null;
		
		try {
			n = new Natural("3.141592653589793238462643383279502884");
		} catch (NumberFormatException e) {
			nfe = e;
		}
		
		if (nfe == null)
			System.out.println("Failed");
		else
			System.out.println("Success");
	}

}