1 import java.util.Scanner;
 2 
 3 public class sqrtNewton {
 4     public static void main(String[] args) {
 5         System.out.println("请输入要开方的数：");
 6         Scanner input = new Scanner(System.in);
 7         double num = input.nextDouble();
 8         double e = 0.01F;
 9         sqrt(num, e);
10         num = 2;
11         e = 0.0001F;
12         sqrt(num, e);
13         num = 2;
14         e = 0.00001F;
15         sqrt(num, e);
16     }
17     private static double sqrt(double num, double e) {
18         double gssn = num / 2;
19         double e0;
20         int cnt = 0;
21         do {
22             gssn= (gssn + num / gssn) / 2;
23             e0 = gssn*gssn - num;
24             cnt++;
25             System.out.printf("尝试 %f, 误差: %f\n", gssn, e0);
26         } while (e0 > e);
27 
28         System.out.printf("尝试 %d 次, 结果为: %f\n", cnt, gssn);
29         return gssn;
30     }
31 }