11 数的整数次方

public class test11{
    private static boolean invalidInput = false;//指示输入是否非法
    public static double power(double base, int exponent){
        if(base>-0.0000001&&base<0.0000001){//判断是否为0
            if(exponent<0){
                invalidInput = true;//输入非法
            }
            return 0;
        }
        if(exponent<0){
            return 1/powerWithUnsignedExponent(base,-exponent);
        }
        return powerWithUnsignedExponent2(base,exponent);
    }
    //循环
    private static double powerWithUnsignedExponent(double base, int absExponent) {
        double result = 1.0;
        for(int i=1;i<=absExponent;i++){
            result = result * base;
        }
        return result;
    }
    //递归
    private static double powerWithUnsignedExponent2(double base, int absExponent) {
        if(absExponent==0) return 1;
        if(absExponent==1) return base;
        double result = powerWithUnsignedExponent2(base,absExponent>>1);
        result *= result;
        if((absExponent&1)==1){
            result *= base;
        }
        return result;
    }

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