045_循环的注意事项和练习题

package com.atguigu.chapter04.myfor

object usefor2 {
  def main(args: Array[String]): Unit = {
    for (i <- 1 to 3; j = i * 2) {
      println(" i= " + i + " j= " + j)
    }

    //等价
    println("------------------------")
    for {
      i <- 1 to 3
      j = i * 2} {
      println(" i= " + i + " j= " + j)
    }

  }
}

注意事项

package com.atguigu.chapter04.myfor

object stepfor {
  def main(args: Array[String]): Unit = {

    for (i <- 1 to 10) {
      println("i=" + i)
    }
    //步长控制为2
    println("---------------------")
    //Range(1,10,2)的对应的构建方法是
    //def apply(start: Int, end: Int, step: Int): Range = new Range(start, end, step)
    for (i <- Range(1, 10, 2)) {
      println("i=" + i)
    }

    //控制步长的第二种方式-for循环守卫.
    // 不用range() 也可以控制
    // 使用 取模 %
    println("---------------------")
    for (i <- 1 to 10 if i % 2 == 1) {
      println("i=" + i)
    }
  }
}

这种步长不就是python的写法么

package com.atguigu.chapter04.myfor

object ForExercise01 {
  def main(args: Array[String]): Unit = {
    /*
    for循环练习题

     打印1-100之间所有是9的倍数的整数的个数及总和
     完成下面的表达式输出

     */
    val start = 1
    val end = 100
    var count = 0
    var sum = 0
    for (i <- start to end) {
      if (i % 9 == 0) {
        count += 1
        sum += i
      }
    }
    printf("count=%d, sum=%d\n", count, sum)

    //输出加法循环表达式吧
    val num = 6
    for (i <- 0 to num) {
      printf("%d + %d = %d\n", i, (num - i), num)
    }


    var list = List(1,2)
  }
}

count=11, sum=594
0 + 6 = 6
1 + 5 = 6
2 + 4 = 6
3 + 3 = 6
4 + 2 = 6
5 + 1 = 6
6 + 0 = 6

Process finished with exit code 0