Authors:
Stuart Reges, Marty Stepp
Chapter:
Recursion
Exercise:
Exercises
Question:8 | ISBN:9780136091813 | Edition: 2
Question
Write a recursive method called multiplyEvens that returns the product of the first n even integers. For example, multiplyEvens(1) returns 2 and multiplyEvens(4) returns 384 (because 2 * 4 * 6 * 8 = 384). The method should throw an IllegalArgumentException if it is passed a value less than or equal to 0.
Answer
package recursion;
public class MultiplyOfEvens {
public static int multiplyEvens(int value) {
// throws illegalArgumentException if the value less than or equls zero
if (value <= 0)
throw new IllegalArgumentException();
// return 2 if the value equals 1
if (value == 1)
return 2;
else {
return 2 * value * multiplyEvens(value - 1);
}
}
public static void main(String[] args) {
System.out.println("multiply of evens is: "+multiplyEvens(4));
}
}
Output:
multiply of evens is: 384