projecteuler Sum square difference

The sum of the squares of the first ten natural numbers is,

1² + 2² + ... + 10² = 385

The square of the sum of the first ten natural numbers is,

(1 + 2 + ... + 10)² = 55² = 3025

Hence the difference between the sum of the squares of the first ten natural numbers and the square of the sum is 3025 − 385 = 2640.

Find the difference between the sum of the squares of the first one hundred natural numbers and the square of the sum.

译文：

自然数1到10的平方之和为385，他们的和的平方为3025，现将自然数1到10的和的平方减去平方之和等于2640，求出自然数从1到100的和的平方减去平方之和。

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第一次code:

 public class Main
 {
     public static void main(String[] args)
     {
         System.out.println(start(100)-run(100));
     }
     /**
      * 求前N项平方之和
      * @param n
      * @return
      */
     public static int run(int n)
     {
         int m=0;
         for(int i=0;i<n+1;i++)
         {
             m += i*i;
         }
         return m;
     }
     /**
      * 求前N项和的平方
      * @param n
      * @return
      */
     public static int start(int n)
     {
         int m=0,o=0;
         for(int i=0;i<n+1;i++)
         {
             m += i;
         }
         o = m*m;
         return o;
     }
 }