scala-map

import scala.collection.immutable.HashMap
//immutable不可变map
import scala.collection.mutable.Map
//immutable可变map

//1
var m1 = Map("a" -> 1, "b" -> 2)

m1 += ("c" -> 3, "d" -> 4)
println(m1.get("d"))
m1 -= "d"

for ((k, v) <- m1) print("k:" + k + "  v:" + v) //遍历k和v
for (k <- m1.keySet) print("key:" + k) //遍历k
for (v <- m1.values) print("value:" + v) //遍历v


//yield关键字用于在for循环，每一步记录下当前的状态并保存，最后输出新的集合
var new_map = for ((k, v) <- m1) yield (v, k) // 反转key和value生成新的map

for ((k, v) <- new_map) print("  新map  k:" + k + "  v:" + v) //遍历新map


println(m1("c"))
println(m1.get("d"))
//val hi1 = m1.getOrElse("c")
//println(hi1)

//2
var hm1 = HashMap("a" -> 1, "b" -> 2)

var hm2 = hm1 + ("c" -> 3, "d" -> 4)

var i = hm2.get("d")
println(i)

var ary1 = Array(1, 2, 3).map((x0: Int) => 3 * x0)
for (item <- 0 until ary1.length) {
  println(ary1(item))
}
//函数仅仅包含一个参数，并且在右侧x0如果只使用1次则可以使用“_”代表x0
var ary2 = Array(3, 5, 7).map(_ * 3)
for (item <- 0 until ary2.length) {
  println(ary1(item))
}