PowerImpl.java

public class PowerImpl {
    static int power(int x, int y) {
        // base case
        if (y == 0) {
            return 1;
        }
        int temp = power(x, y / 2);
        if (y % 2 == 0) {
            return temp * temp;
        } else {
            return x * temp * temp;
        }
    }

    public static void main(String[] args) {
        System.out.println(power(2, 10));
        System.out.println(power(-2, 9));
    }
}