markdown 斯卡拉警告

Posted 2021-05-06

## val
- val should be initialized and couldn't change
  ```scala
  val x
  // error: '=' expected but ';' found.
  
  val x = 5
  x = 6
  // It couldn't change
  ```
  
## scope
- The val or var in {} couldn't be used out of {}
  ```scala
  {
    val x = 5
  }
  println(x)
  // x is not value
  ```

## Pattern matching
- Case is checked from first
- Case could be used in multiline
  ```scala
  val x = 1
  x match {
    case 1 =>
      println("1")
      println("OK")
    case _ =>
      println("NOT 1")
  }
  // 1
  // OK
  ```