CareerCup

10^23 is not divisible by 7.

public class Amazon {

	private static class NineSet {
		
		private int current = 0;
		
		public NineSet() {
			super();
		}

		public int next() {
			current = next(current);
			return current;
		}
		
		private int next(int n) {
			int r = n;
			if (n%10 == 0) {
				r += 9;
			} else {
				r = 10*next(n/10);
			}
			return r;
		}
	}
	
	public static int getMultipleOf(int q) {
		NineSet nine = new NineSet();
		while(true) {
			int n = nine.next();
			if (n%q == 0) return n;
		}
	}
	
	public static void main(String[] args) {
		System.out.println(getMultipleOf(2)); // => 90
		System.out.println(getMultipleOf(10));// => 90
		System.out.println(getMultipleOf(7)); // => 9009
	}

}

better to do this in the next method

private int next(int n) {
			if (n%10 == 0) {
				n += 9;
			} else {
				n = 10*next(n/10);
			}
			return n;
		}