class Dome_For2{
  public static void main(String[] args) {
    //System.out.println("Hello World!");
    //求1-10的偶数的和
    int sum = 0;
    for (int i = 1;i<=10 ; i++ ) {
      if (i%2 ==0) {      //判断语句
        sum +=i;      //求和
      }
    }
    System.out.println(sum);
  }
}

class Demo_While {
  public static void main(String[] args) {
    //求1-100之和
    int sum = 0;          //定义初始和为0
    int i = 1;            //定义开始求和的第一个数
    while (i <= 100) {        //判断条件语句
      sum += i;          //sum = sum + i;
      i++;            //让变量i自增
    }
    System.out.println("sum = " + sum);
  }
}

class Demo1_DoWhile {
  public static void main(String[] args) {
    //求1-100的和
    int sum = 0;                //定义变量sum,用于存储求和的值
    int i = 1;                  //定义变量i
    do {                     // do 就是 干
      //System.out.println("i = " + i);       //循环体语句
      sum +=i;
      i++;
    }
    while (i <= 100);              //判断条件语句
    System.out.println("sum = "+sum);      //输出结果
    }
  }