i could not get the recursion in java

[sivasayanth]

I have just studied one java source code. That entirely belongs to recursion in java. However, I could not understand what happened in the execution sequence.

Code:

public class MainClass {
  public static void main(String[] args) {
    double x = 5.0;
    System.out.println(x + " to the power 4 is " + power(x, 4));
    System.out.println("7.5 to the power 5 is " + power(7.5, 5));
    System.out.println("7.5 to the power 0 is " + power(7.5, 0));
    System.out.println("10 to the power -2 is " + power(10, -2));
  }

  // Raise x to the power n
  static double power(double x, int n) {
    if (n > 1)
      return x * power(x, n - 1); // Recursive call
    else if (n < 0)
      return 1.0 / power(x, -n); // Negative power of x
    else
      return x;
  }
}

Please help me.
What is the return value When first execution happened?

[Eranga]

Initially x = 5.0

Code:

double x = 5.0;

Call the power() with x = 5.0 and n = 4. Those parameters are moving on the loop as follows.

Code:

on if clause - still n > 1(n = 4) so,
       return 5.0 * power( 5.0, 3)

on if clause - still n > 1(n = 3) so,
        5.0 * return 5.0 * power( 5.0, 2)

on if clause - still n > 1(n = 3) so,
        5.0 * 5.0 * return 5.0 * power( 5.0, 1) 

skip else-if clause - n is not a negative

on else clause
      5.0 * 5.0 * 5.0 * return 5.0

So the answer is 625.0 for the first println(). Hope it's help

[sivasayanth]

Thanks a lot Eranga.

if we take the visual of above code.it is chain loop. is it Eranga?

[Eranga]

Yes, kind of a chain loop. Simply do the same process(what we called looping) until certain condition is satisfied and keep track of certain data.

Here you can see that the value of x behave like that.