// prints result of base to whatever non-negative integer power
// Beth Katz - April 2008

import java.util.NoSuchElementException;
import java.util.Scanner;

public class Power {

	public static void main(String[] args) {
		Scanner console = new Scanner(System.in);
		
		System.out.println("Enter base (double) and exponent (int >= 0):");
		try {
			while (console.hasNextDouble( )) {
				double base = console.nextDouble( );
				int expo = console.nextInt( );
				if (expo < 0) {
					System.out.println("Exponent must be >= 0 but is " + expo);
				} else {
					System.out.println( );
					System.out.println(base + " to the " + expo 
							+ " power is " + power(base, expo));
				}
			}
		}
		catch (NoSuchElementException e) {
			System.out.println("Bad input");
		}
	}
	
	// return base to the expo power
	private static double power(double base, int expo) {
	   if (0 == expo) {
	        return 1.0;
	   } else if ((expo % 2) == 0) { // even expo
			double powerPart = power(base, expo/2); 
	        return powerPart * powerPart;
	   } else { // odd expo
			return base * power(base, expo-1);
	   }
	}

}