A detailed example of java square root of sqrt algorithm

Square root (sqrt) algorithm in java

The square root (sqrt, square root) is a common mathematical formula in mathematics;

There are two steps to find the square root by using the program:

Step 1: while() loop, control the number of loops and the number of decimal places, prevent infinite loop and the occurrence of multiple decimal places;

Step 2: By decomposing the square root, using a loop, gradually reduce to close to the square root;

Similarly, other square roots can be similarly extended, but it's important to note that,
You want to make sure that you put in a positive number;
The odd power square root should be converted to a positive number to ensure the cyclic convergence, and then the positive and negative judgment of the results should be made.

The code is as follows:

/* 
 * Algorithms.java 
 * 
 * Created on: 2013.12.03 
 *   Author: Wendy 
 */ 
 
/*eclipse std kepler, jdk 1.7*/ 
 
public class Algorithms  
{ 
  public static double sqrt(double c) 
  { 
    if(c<0) return Double.NaN; //NaN: not a number 
    double err = 1e-15; // minimum  
    double t = c; 
    while (Math.abs(t-c/t) > err*t) //t^2 Close to the c,  To prevent the decimal  
      t = (c/t + t)/2.0; 
    return t; 
  } 
   
  public static double cbrt(double c) 
  { 
    boolean b = (c>0) ? true : false; // save c The symbol of  
    c = (c>0) ? c : -c; 
    double err = 1e-15; 
    double t = c; 
    while(Math.abs(t*t-c/t) > err*t) 
      t = (c/(t*t)+t)/2.0; 
    t = (b) ? t : -t; 
    return t; 
  } 
   
  public static void main(String[] args)  
  { 
    double r = sqrt(4.0); 
    System.out.println("sqrt(4.0) = " + r); 
    double rc = cbrt(-27.0); 
    System.out.println("cbrt(9.0) = " + rc); 
  } 
} 

Output:

sqrt(4.0) = 2.0 
cbrt(9.0) = -3.0 

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