请各位给俺看看这道java道;

jaybeyond

public class PowerCalc
{
  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 n == 0 ? 1.0 : x;   // When n is 0 return 1, otherwise x
  }
}



最后的结果是:
5.0 to the power 4 is 625.0
7.5 to the power 5 is 23730.46875
7.5 to the power 0 is 1.0
10 to the power -2 is 0.01

为什么会是这样的结果,我想他们的结果应该都是1.0,在power自身调用自身时,他应该没有返回值,直到最后n的值到0的时候才有返回值?但是每次返回一个自身x的值后再*以以前的值,不明白,那们大大能给指点一下吗???谢谢先!!!

javaguo

递归调用。
举第一个 power(x,4)为例子：

power(x,4)     n=4>1     返回x*(power(x,3))
power(x,3)     n=3>1     返回x*(power(x,2))
power(x,2)     n=2>1     返回x*(power(x,1))
power(x,1)     n=1         返回x
从下往上计算x*x*x*x=5*5*5*5=625，

jaybeyond

噢,原来是这样的..