Spark记录-Scala shell命令

1.scala shell命令

scala> :help
All commands can be abbreviated, e.g., :he instead of :help.
:edit <id>|<line>        edit history
:help [command]          print this summary or command-specific help
:history [num]           show the history (optional num is commands to show)
:h? <string>             search the history
:imports [name name ...] show import history, identifying sources of names
:implicits [-v]          show the implicits in scope
:javap <path|class>      disassemble a file or class name
:line <id>|<line>        place line(s) at the end of history
:load <path>             interpret lines in a file
:paste [-raw] [path]     enter paste mode or paste a file
:power                   enable power user mode
:quit                    exit the interpreter
:replay [options]        reset the repl and replay all previous commands
:require <path>          add a jar to the classpath
:reset [options]         reset the repl to its initial state, forgetting all session entries
:save <path>             save replayable session to a file
:sh <command line>       run a shell command (result is implicitly => List[String])
:settings <options>      update compiler options, if possible; see reset
:silent                  disable/enable automatic printing of results
:type [-v] <expr>        display the type of an expression without evaluating it
:kind [-v] <expr>        display the kind of expression's type
:warnings                show the suppressed warnings from the most recent line which had any

2.scala基本类型

3.常用特殊字符

\n 换行符，其Unicode编码为 (\u000A) 
\b 回退符，其Unicode编码为 (\u0008) 
\t tab制表符 ，其Unicode编码(\u0009) 
\” 双引号，其Unicode编码为 (\u0022) 
\’ 单引号，其Unicode编码为 (\u0027) 
\ 反斜杆，其Unicode编码为(\u005C)

4.函数

 5.类

//采用关键字class定义

class Person {

//类成员必须初始化，否则会报错

//这里定义的是一个公有成员

var name:String=null

}

附录：

import java.sql.{ Connection, DriverManager }
import java.util.{Date, Locale}
import java.text.DateFormat
import java.text.DateFormat._
object Mysql extends App {
 // def main(args: Array[String]): Unit = {
    // 访问本地MySQL服务器，通过3306端口访问mysql数据库
    val url = "jdbc:mysql://localhost:3306/mysql"
    //驱动名称
    val driver = "com.mysql.jdbc.Driver"
    //用户名
    val username = "root"
    //密码
    val password = "1"
    //初始化数据连接
    var connection: Connection = _
    try {
      //注册Driver
      Class.forName(driver)
      //得到连接
      connection = DriverManager.getConnection(url, username, password)
      val statement = connection.createStatement
      //执行查询语句，并返回结果
      val rs = statement.executeQuery("SELECT host, user FROM user")
      //打印返回结果
      while (rs.next) {
        val host = rs.getString("host")
        val user = rs.getString("user")
        println("host = %s, user = %s".format(host, user))
      }
    } catch {
      case e: Exception => e.printStackTrace
    }
    //关闭连接，释放资源
    connection.close
    //for循环
    var myArray: Array[String] = new Array[String](10);
    for (i <- 0 until myArray.length) {
      myArray(i) = "value is: " + i;
    }
    for (value: String <- myArray) {
      println(value);
    }
    for (value: String <- myArray if value.endsWith("5")) {
      println(value);
    }
  val now = new Date
  val df = getDateInstance(LONG, Locale.FRANCE)
  println(df format now)
  //}
  val greetStrings =new Array[String](3)
  greetStrings(0)="Hello"
  greetStrings(1)=","
  greetStrings(2)="world!\n"
  greetStrings.update(0,"Hello")
  greetStrings.update(1,",")
  greetStrings.update(2,"world!\n")
  for(i <- 0 to 2)
    print(greetStrings(i))
  val oneTwo = List(1,2)
  val threeFour = List(3,4)
  val oneTwoThreeFour=oneTwo ::: threeFour
  println (oneTwo + " and " + threeFour + " were not mutated.")
  println ("Thus, " + oneTwoThreeFour + " is a new list")
  //几种循环
  def printArgs ( args: Array[String]) : Unit ={
    var i=0
    while (i < args.length) {
      println (args(i))
      i+=1
    }
  }
  def printArgs1 ( args: Array[String]) : Unit ={
    for( arg <- args)
      println(arg)
  }
  def printArgs2 ( args: Array[String]) : Unit ={
    args.foreach(println)
  }
  //类与对象
  class ChecksumAccumulator{
    private var sum=0
    def add(b:Byte) :Unit = sum +=b
    def checksum() : Int = ~ (sum & 0xFF) +1
  }
  def gcdLoop (x: Long, y:Long) : Long ={
    var a=x
    var b=y
    while( a!=0) {
      var temp=a
      a=b % a
      b = temp
    }
    b
  }
}