Scala

package com.test.chapter04

import scala.io.StdIn

object Test01_IfElse {
  def main(args: Array[String]): Unit = {
    println("请输入您的年龄：")
    val age: Int = StdIn.readInt()

    //1.单分支
    if (age >= 18){
      println("成年")
    }
    println("==========================================")

    //2.双分支
    if (age >= 18){
      println("成年")
    } else {
      println("未成年")
    }
    println("==========================================")

    //3.多分支
    //分支语句的返回值
    val reslut: String = if (age <= 6){
      println("童年")
      "童年"
    } else if(age < 18){
      println("青少年")
      "青少年"
    } else if(age < 35){
      println("青年")
      "青年"
    } else if(age < 60){
      println("中年")
      "中年"
    } else {
      println("老年")
      "老年"
    }
    println("result: " + reslut)
    println("===============================================")

    //java中三元运算符 a?b:c
    val res: String = if (age >= 18){
      "成年"
    } else {
      "未成年"
    }

    val res2 = if (age >= 18) "成年" else "未成年"
    println("=============================================")

    // 5. 嵌套分支
    if (age >= 18){
      println("成年")
      if (age >= 35){
        if (age >= 60){
          println("老年")
        } else {
          println("中年")
        }
      } else {
        println("青年")
      }
    } else {
      println("未成年")
      if (age <= 6){
        println("童年")
      } else {
        println("青少年")
      }
    }


  }

}

package com.test.chapter04

object Test02_ForLoop {
  def main(args: Array[String]): Unit = {
    //java for语法: for(int i = 0; i < 10; i++){System.out.println(i + ". hello world")}

    //范围遍历
    for (i <- 1 to 10){
      println(i + ". hello world")
    }
    for (i <- 1.to(10)){
      println(i + ". hello world")
    }

    println("=======================================")
//    for (i <- Range(1, 10)){
//      println(i + ". hello world")
//    }
    for (i <- 1 until 10){
      println(i + ". hello world")
    }
    println("======================================")

    // 2.集合遍历
    for (i <- Array(12, 34, 53)){
      println(i)
    }
    println("======================================")

    // 3.循环守卫
    for (i <- 1 to 10){
      if (i != 5){
        println(i)
      }
    }

    for (i <- 1 to 10 if i != 5){
      println(i)
    }
    println("==========================================")

    //4. 循环步长
    for (i <- 1 to 10 by 2){
      println(i)
    }
    println("============================================")

    for (i <- 13 to 30 by 3){
      println(i)
    }
    println("============================================")

    for (i <- 30 to 13 by -2){
      println(i)
    }

    println("============================================")

    for (i <- 1 to 10 reverse){
      println(i)
    }
    println("-===============================================")

    for (i <- 1.0 to 10.0 by 0.5){
      println(i)
    }
    println("==============================================")

    //5. 嵌套循环
    for (i <- 1 to 3){
      for (j <- 1 to 3){
        println("i = " + i + ", j = " + j)
      }
    }

    println("==========================================")
    for (i <- 1 to 4; j <- 1 to 5){
      println("i = " + i + ", j = " + j)
    }

  }

}

package com.test.chapter04

//输出九九乘法表
object Test03_Practice_MulTable {
  def main(args: Array[String]): Unit = {
    for (i <- 1 to 9){
      for (j <- 1 to i){
        print(s"$j * $i = ${i * j} t")
      }
      println()
    }

    // 简写
    for (i <- 1 to 9; j <- 1 to i){
      print(s"$j * $i = ${i * j} t")
      if (j == i) println()
    }
    println("=====================================")

    //6. 引入变量
    for (i <- 1 to 10){
      val j = 10 - i
      println("i = " + i + ", j = " + j)
    }
    println("=======================================")

    for (i <- 1 to 10; j = 10 - i){
      println("i = " + i + ", j = " + j)
    }
    println("=======================================")

    //6. 循环返回值
    val a = for (i <- 1 to 10){
      println(i)
    }
    println("a = " + a)

    println("=======================================")

    val b = for (i <- 1 to 10) yield i * i
    println("b = " + b)

  }
}

package com.test.chapter04

// 打印输出一个九层塔
object Test04_Practice_Pyramid {
  def main(args: Array[String]): Unit = {
    for (i <- 1 to 9){
      val stars = 2 * i -1
      val spaces = 9 - i
      println(" " * spaces + "*" * stars)
    }
    println("======================================")

    for (i <- 1 to 9; stars = 2 * i -1; spaces = 9 - i){
      println(" " * spaces + "*" * stars)
    }
    println("======================================")

    for (stars <- 1 to 17 by 2; spaces = (17 - stars) / 2){
      println(" " * spaces + "*" * stars)
    }
  }

}

package com.jny.chapter04

object Test05_WhileLoop {
  def main(args: Array[String]): Unit = {
    //while
    var a: Int = 10
    while (a >= 1){
      println("this is a while loop: " + a)
      a -= 1
    }

    var b: Int = 0
    do {
      println("this is a do-while loop: " + b)
      b -= 1
    } while (b > 0)
  }

}

package com.test.chapter04

import scala.util.control.Breaks
import scala.util.control.Breaks._

object Test06_Break {
  def main(args: Array[String]): Unit = {
    //1. 采用抛出异常的方式，退出循环
    try{
      for (i <- 0 until 5){
        if (i == 3)
          throw new RuntimeException
          println(i)
        }
      } catch {
        case e: Exception => //什么都不做，只是退出循环
      }

      //2.使用scala中的breaks类的的break方法，实现异常的抛出和捕捉
    Breaks.breakable(
      for (i <- 0 until 5){
        if (i == 3)
          Breaks.break()
        println(i)
      }
    )

    breakable(
      for (i <- 0 until 5){
        if (i == 3)
          break()
        println(i)
      }
    )
      println("这是循环外的代码")
    }
  }