Scala 集合
//yield,产生新集合
for(i <- 1 to 5) yield i * 2
//定义函数
def add(a:Int,b:Int):Int = a + b
//定义函数，实现n的阶乘
5! = 5 x 4x 3x 2x 1 ;
def fac(n:Int) = {
var r = 1
for(i <- 1 to n){
r *= i
}
r
}
//递归函数必须显式定义返回类型
def fac(n:Int):Int = if(n == 1) 1 else n * fac(n - 1)
//定义函数，参数数带有默认值
def decorate(prefix:String="{{{",str:String,suffix:String="}}}") = {
prefix + str + suffix
}
//带名参数
decorate(str = "hello" )
//变长参数
def add(x:Int*) = {var sum = 0 ;for(i <- x)sum += i ;sum}
add(1,2,3,4,5)
add(1 to 5:_*) //把range对象打散成数字序列,1,5
//过程，没有=的函数,
def out(){println("hello world")}
//lazy，延迟计算
val x = 1/ 0
lazy val x = 1 / 0
x
//定义数组 [泛型]
val arr = new Array[Int](10)
arr(0) = 1
arr(1) = 2
arr(2) = 3
for(i <- 0 until arr.length ) arr(i) = i + 1
val arr = Array[String]("hello","world")
val arr = Array("hello","world")
val arr = Array.apply("hello","world")
val arr = Array.apply[String]("hello","world")
val arr = Array[Int](100) //一个100的值
val arr = new Array[Int](100) //100个0
//命名法则:
//++ 加多个元素
//+ 加一个元素
//+= =表示修改自身的内容
//数组缓冲区(集合)
//=修改自身的内容,否则生成新集合
import scala.collection.mutable.ArrayBuffer
val buf = ArrayBuffer[Int](1,3)
val x = buf.++(4 to 10)
buf.++=(4 to 10)
buf.+=(1,4) //追加多个元素
buf += 12
buf.trimEnd(3) //移除末尾3个元素
buf.insert(0,-2,-1,0) //在指定的索引位置，插入数字序列
buf.toArray()
//倒序遍历
for(i <- (0 until buf.length).reverse) println(buf(i))
//常用操作
buf.sum
//mkStrig,连接元素成串
buf.mkString(",")
buf.mkString("{{{",","}}}")
//多维数组
val arr = new Array[Array[Int]](2)
val arr = Array.ofDim[Int](3,4)
//java集合和scala buffer之间的互操作
val list:java.util.List[String] = new java.util.ArrayList[String]()
list.add("hello")
list.add("world")
//定义函数，使用java的list类型
def mylist(list:java.util.List[String]) = println(list.size())
val buf = ArrayBuffer[String]("how","are","you")
mylist(buf) //类型不匹配
import scala.collection.JavaConversions.bufferAsJavaList
mylist(buf) //ok
//定义scala参数缓冲区的函数
def mybuf(buf:scala.collection.mutable.Buffer[String]) = println(buf.size())
import scala.collection.JavaConversions.asScalaBuffer //隐式转换
mybuf(list);
//映射map,不可变
val map = Map(1->"tom",2->"tomas",3->"tomasLee")
map(1)
map(2)
map(3)
//可变集合,导类指定别名
import scala.collection.mutable.{Map=>MMap}
val map = MMap(1->"tomas",2->"tomasLee")
map(1)
//对偶是一个kv对，等价于java Map中Entry.
val c = 100->"tomas"
val c = (100,"tomas")
//map
val map = MMap(("001","tom"),("002","tomas"),("003","tomasLee"))
//迭代map
for(k <- map.keys) println(k)
for(v <- map.values) println(v)
for((k,v) <- map) println(k + " : " + v)
for(c <- map) println(c._1 + " : " + c._2)
//
map.contains("001")
val v = map.getOrElse("001","nobody")
map.+=(( "006","tom6"))
map.+=("006"->"tom6")
map.-=("006")
val m1 = scala.collection.immutable.SortedMap(1->"tom1",3->"tom3",2->"tom2")
for(c <- m1) println(c)
//元组tuple
val t = ( 1,"tom",12)
val t:Tuple3[Int,String,Int] = new Tuple3[Int,Int](1,12) ;
t._1
t._1 = 100 //错的,元组的组员是不能重新赋值
//拉链 zipval ids = (1,3)val names= ("tom1","tom2","tom3")ids.zip(names)ids.zipAll(names,"nobody") //全拉链,-1左边填充元素，"nobody"右侧填充元素
