443: Mainline

Now you are ready to perform the recursion trick: You replace the call to powerOf2 in recursivePowerOf2 by a call to recursivePowerOf2 itself:

public static int recursivePowerOf2 (int n) {
 if (n == 0) {return 1;}
 else {
  return 2 * recursivePowerOf2(n - 1); 
 } 
} 

The new version works for two reasons:

• If the value of the parameter, n, is 0, recursivePowerOf2 returns 1.
• If the value of n is not 0, recursivePowerOf2 asks itself to compute the power of 2 for a number that is 1 less than the value of n. Then, recursivePowerOf2 may ask itself to compute the power of 2 for a number that is 2 less than the original value of n, and so on, until the recursivePowerOf2 needs to deal with only 0.