java用级数求双精度的平方根

Question

问题是：

Using the following approximate formula, write a function or method that returns the square root of a real number! Use the sequence x[k + 1] = 1/2 * (x[k] + a / x[k]), which is converges to a square root of 'a' real parameter if x1 = 1.

我的解决方案与此类似，但没有使用以下公式：

public static double squareRoot(double a) {

    double k; 
    double root = a / 2;
    do {
        k = root;
        root = 0.5*(k+ (a / k));
    } while ((k - root) != 0);

    return root;`
}