Answer to Question #289371 in Java | JSP | JSF for asjkdhjka

Question

1. Write a recursive function, power, that takes as parameters two integers x and y such that x is nozero and return x^y. You can use the following recursive function definition to calculate x^y.

               If y>= 0,

 

     1 if y=0

power(x, y) =     x if y=1

     x*power(x,y-1) if y>1

 

         if y<0,

power(x, y) = 1/power(x, -y)

 

Write a TestPower class that call addRecur method. You should provide the user to enter integer to calculate its total. The method should throw an IllegalArgumentException if it is passed a value other than integer.

Answer 1

import java.util.*;


public class App {


	/**
	 * The start point of the program
	 * 
	 * @param args
	 * 
	 */
	public static void main(String[] args) {
		Scanner keyBoard = new Scanner(System.in);


		try {
			System.out.print("Enter x: ");
			String xString = keyBoard.nextLine();
			int x = Integer.parseInt(xString);
			System.out.print("Enter y: ");
			String yString = keyBoard.nextLine();
			int y = Integer.parseInt(yString);
			try {
				System.out.println(x + "^" + y + " = " + power(x, y));
			} catch (IllegalArgumentException e) {
				System.out.println("IllegalArgumentException");
			}


		} catch (NumberFormatException e) {
			System.out.println("Not a valid integer values.");
		}


		keyBoard.close();
	}


	public static double power(int x, int y) throws IllegalArgumentException {


		if (y == 0) {
			return 1;
		}
		if (y < 0) {
			return 1 / Math.pow((double) x, (double) -y);
		}
		return x * Math.pow((double) x, (double) (y - 1));
	}


}