12 求base的exponent次方

给定一个double类型的浮点数base和int类型的整数exponent。求base的exponent次方。

解答：默认0的所有次方都为0（包括0的0次方，和0的负幂次方）
a>>1 表示 a/2
a<<1 表示 a×2

判断奇偶：n%2==1 或 (n&1)==1

public class Test12 {
	//非递归解法
    public double Power(double base, int exponent) {
        double result = 1.0;
        if (exponent == 0) {
            return 1.0;
        }
        if (base > -0.00001 && base < 0.00001) {
            return 0;
        }
        if (exponent > 0) {
            for (int i = 0; i < exponent; i++) {
                result = result * base;
            }
        } else {
            exponent = -exponent;
            for (int i = 0; i < exponent; i++) {
                result = result * base;
            }
            result = 1.0 / result;
        }
        return result;
    }
	//递归方式
    public double Power2(double base, int exponent) {
        double result = 1.0;
        if (exponent == 0) {
            return 1.0;
        }
        if (base > -0.00001 && base < 0.00001) {
            return 0;
        }

        if (exponent > 0) {
            result = getResult(base, exponent);
        } else {
            exponent = -exponent;
            result = getResult(base, exponent);
            result = 1.0 / result;
        }
        return result;
    }

    public double getResult(double base, int exponent) {
        if (exponent == 1) {
            return base;
        }
        double result = getResult(base, exponent >> 1);
        result *= result;
        if ((exponent & 1) == 1) {
            result *= base;
        }
        return result;
    }
}