第一课 Scala光速入门
王家林_DT大数据梦工厂http://blog.sina.com.cn/s/blog_686c3cfb0102w4uz.html
要点速记
def sum(numbers : Int*) = { var result = 0; for(element <- numbers) result += element; result}
sum(1 to 100) // erro 1 to 100 => range
sum(1 to 100: _*) //correct
过程: 没有返回值的函数
def morning(content : String){println("Good " + content)}
def morning(content : String): Unit "Good " + content //no return
lazy 只在调用时执行
val arr = new Array[Int](5)
=> Array[Int] = Array(0,0,0,0,0)
val arr1 = Array(0,0,0,0,0) //use the apply method, the same result
Array 不可边长 ArrayBuffer可边长
import scala.collection.mutable.ArrayBuffer
arr = arrBuffer.toArray
arrBuffer = arr.toBuffer
+= 在尾部追加
yield
map
val arr2 = Array(1,1,3,4,10,11,100)
val arr3 = for(i <- arr2 ) yield i*i
arr2.filter(_%3 == 0).map(i => i*i)
.getOrElse("***",#)
作业一: 移除一个数组中第一个负数后的所有负数
val array = Array(1,-2,2,-1,-3,4)
var key = false
val idx = for(i <- 0 until array.length if !false || array(i) >= 0) yield {
if (array(i) < 0) key = true
i
}
for(t <- 0 until idx.length) {array(t) = array(idx(t))}
array.trimEnd(array.length = idx.length)