关于算法:给double类型的数据开根号

须要给double类型的数据开根号
要求精度在0.0001之内

public double getSqrtNum(double num){    double left;    double right;    double mid;    if(n<1&&n>0){        left = num;        right = 1;    }    if(n>1){        left = 0;        right = num;    }    mid = (left+right)/2;    while(Math.abs(mid*mid-n)>0.0001){        if(mid*mid<n){            left = mid;        }else{            right = mid;        }        mid = (left+right)/2;    }    return mid;}