Scala learning (two, control structure)

1. If statement, the whole is the same as C++, I write something that you may not be familiar with.

object HelloWorld {
    
    
    def main(args: Array[String]) {
    
    
      var x = 2
      println(if(x > 0) 1 else -1)
      var s = if(x > 0) 1 else -1
      println(s)
      //甚至用混合类型的
      var a = if(x > 0) "abc" else -1
      println(a)
      //如果else部分缺失，不能直接空
      if(x > 0) 1 else ()
    }
  }

2. Termination statement
Single-line multiple statements: var x = 1; x = x+1 needs to add one;
multiple-line single statement: var x = 1+
2 Here we end with the operator +

3. Block expressions, expressions in {}

import scala.math.sqrt

object HelloWorld {
    
    

    def main(args: Array[String]) {
    
    
     var x = {
    
    var a = 100; sqrt(a)}//只会等于最后一个
      println(x)
    }
  }

4. Input and output
Input: You can use readLine, readBoolean, readInt, etc. to input the corresponding type. But only readLine has a prompt string.

import scala.io.StdIn.readLine
object HelloWorld {
    
    
    def main(args: Array[String]) {
    
    
     var x = readLine("please in")
      println(x)
    }
  }

Output: print() and println(), note that ln is added to wrap. (You can also use c-style output printf)

import scala.io.StdIn.{
    
    readInt, readLine}

object HelloWorld {
    
    
    def main(args: Array[String]) {
    
    
     var x = readInt()
      printf("x is %d",x)
    }
  }

5. Loops, while and do loops are the same as
for loops in previous languages

object HelloWorld {
    
    

    def main(args: Array[String]) {
    
    
     val s = "hello"
      var sum = 0
      for(i <- 0 until s.length)
        sum += s(i)
      println(sum)
    }
  }

Enhanced for loop

object HelloWorld {
    
    
    def main(args: Array[String]) {
    
    
      for(i<- 1 to 3; j<- 1 to 3) println(10*i+j)
    }
  }