17-08-07 计算一个数字的立方根，不使用Math方法

计算一个数字的立方根，不使用Math方法

public static void num() {Scanner scanner = new Scanner(System.in);double num = scanner.nextDouble();if (num == 0) {System.out.println(num);}double num1, num2;num1 = num;num2 = (2 * num1 / 3) + (num / (num1 * num1 * 3));// 利用牛顿迭代法求解while (Math.abs(num2 - num1) > 0.000001) {num1 = num2;num2 = (2 * num1 / 3) + (num / (num1 * num1 * 3));}DecimalFormat df = new DecimalFormat("#.0");System.out.println(Double.parseDouble(df.format(num2)));}