带for循环的累积和

public class Main {

  public static void main(String args[]) {

    int i, n = 10;
    /* 
    *来 自
     时 代 J a v a - N o w J a v a . c o m
    */

    int cumulLoop = 0;

    for (i = 0; i < n; i++) {

      cumulLoop += i;

    }

    int cumul = (n * (n - 1)) / 2; // closed-form solution

    System.out.println(cumulLoop + " closed-form:" + cumul);

  }

}