前缀形式先完成加1;后缀形式会使用变量原来的值
int m = 7;
int n = 7;
int a = 2 * ++m; //now a is 16, m is 8
int b = 2 * n++; //now b is 14, n is 8
前缀形式先完成加1;后缀形式会使用变量原来的值
int m = 7;
int n = 7;
int a = 2 * ++m; //now a is 16, m is 8
int b = 2 * n++; //now b is 14, n is 8