Scala 学习

 ArrayBuffer 相当于ArrayList 是有序的。
val a = ArrayBuffer[Int]()
a: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer()

scala> a+= 1
res4: a.type = ArrayBuffer(1)

scala> a+= 2
res5: a.type = ArrayBuffer(1, 2)

scala> a+= 4
res6: a.type = ArrayBuffer(1, 2, 4)
a+=(3,4,5,7)
res7: a.type = ArrayBuffer(1, 2, 4, 3, 4, 5, 7)

a.trimEnd(n)移除a 元素里面最后的n个值

res7: a.type = ArrayBuffer(1, 2, 4, 3, 4, 5, 7)

scala> a.trimEnd(3)

scala> a
res9: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1, 2, 4, 3)

a.remove(n,m) : 移除第n个下标起的，m个元素

scala> a
res11: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1, 2, 4, 3, 10, 2, 3, 4, 5)

scala> a.remove(2,2)

scala> a
res13: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1, 2, 10, 2, 3, 4, 5)

 遍历数组

res14: Array[Int] = Array(1, 2, 3, 4, 5, 6, 7, 8)

scala> for (i <- 0 until (arr.length,2)){
     | println(arr(i))
     | }
1
3
5
7

 映射

scala> val m = Map("a" ->1, "b"->2, "c"->5)
m: scala.collection.mutable.Map[String,Int] = Map(b -> 2, a -> 1, c -> 5)

scala> for ((k,v) <- m) yield (v,k)
res18: scala.collection.mutable.Map[Int,String] = Map(2 -> b, 5 -> c, 1 -> a)　　

 元组