//对Array进行转换，获取的还是Aarry
val a = Array(1,2,3,4,5)
val a2 = for(ele <- a) yield ele * ele

//对ArrayBuffer进行转换，获取的还是ArrayBuffer
val b = ArrayBuffer[Int]()
b+=(1,2,3,4,5)
val b2=for(ele <- b) yield ele*ele
//结合if守卫， 仅转换需要元素
val a3= for(ele <- b if ele % 2==0) yield ele*ele
//使用函数式编程转换数组（通常会用第一种方式）
a.filter(_%2==0).map(2*_)
a.filter{_%2==0}.map{2*_}