Recursive structure

Recursive structure consists of two parts ：

• Define recursive headers .  solve ： When not to call your own methods . If there is no head , Will fall into a dead cycle , That is, the end condition of recursion .
• Recursive body .  solve ： When do I need to call my own methods .
• Example ： Use recursion to find n

• public class Test22 {
      public static void main(String[ ] args) {
          long d1 = System.currentTimeMillis();  
          factorial(10);
          long d2 = System.currentTimeMillis();
          System.out.printf(" Recursive time-consuming :"+(d2-d1));  // Time consuming ：32ms
      }
      /**  The way to find factorial */
      static long  factorial(int n){
          if(n==1){// Recursive header 
              return 1;
          }else{// Recursive body 
              return n*factorial(n-1);//n! = n * (n-1)!
          }
      }
  }

  The execution result is shown in the figure ：

• 

  

  The flaw of recursion

  Simple algorithm is one of the advantages of recursion . But recursive calls take up a lot of system stack , Memory consumption , When there are many levels of recursive calls, the speed is much slower than the loop , So be careful when using recursion .