标签：lex 开发 number vector color break tuple try nts
大体与java相当。scala没有三元表达式。
val num = if(1>0) 1 else 0 //相当于匿名函数 println(num) var num2 = 0 if(1>0) num2 = 1 else num2 = 0 println(num2)
match。与java的stiwch相当。但scala的match强大很多。
通配符匹配（Wildcard Pattern Matching ）
常量匹配 （Constant Pattern Matching ）
变量匹配（Variable Pattern Matching ）
构造函数匹配（Constructor Pattern Matching ）
集合类型匹配（Sequence Pattern Matching ）
元祖类型匹配（Tuple Pattern Matching ）
类型匹配（Typed Pattern Matching ）
// constant patterns case 0 => "zero" case true => "true" case "hello" => "you said ‘hello‘" case Nil => "an empty List" // sequence patterns case List(0, _, _) => "a three-element list with 0 as the first element" case List(1, _*) => "a list beginning with 1, having any number of elements" case Vector(1, _*) => "a vector starting with 1, having any number of elements" // tuples case (a, b) => s"got $a and $b" case (a, b, c) => s"got $a, $b, and $c" // constructor patterns case Person(first, "Alexander") => s"found an Alexander, first name = $first" case Dog("Suka") => "found a dog named Suka" // typed patterns case s: String => s"you gave me this string: $s" case i: Int => s"thanks for the int: $i" case f: Float => s"thanks for the float: $f" case a: Array[Int] => s"an array of int: ${a.mkString(",")}" case as: Array[String] => s"an array of strings: ${as.mkString(",")}" case d: Dog => s"dog: ${d.name}" case list: List[_] => s"thanks for the List: $list" case m: Map[_, _] => m.toString // the default wildcard pattern case _ => "Unknown"
while
do while
与java相同。
for 可以多重循环，循环过滤。返回值。
val list = List("3423")
for(t <- list){
println(t)
}
for(i <- 1 to 10){//包含10
println(i)
}
for(i <- 1 until 10){//不包含10
println(i)
}
println("===================")
for(i <- 1 to 10;if i> 5){//添加过滤条件
println(i)
}
println("===================")
for(i <- 1 to 10;j <- 1 to 10){
println(i +" " + j)
}
println("===================")
for (i <- 1 to 5) yield i * 2
var result = for(t <- list) yield t //result = list
var result2 = for(t <- list) yield t + "10"
result.foreach(println)
try{ }catch{ case ex : NullPointerException => ex.printStackTrace() case _: Exception => "" }
scala没有这两个关键字。但是scala提供了Breaks类来达到相同的效果。
def continue() { for (i <- 1 to 10) { Breaks.breakable({ if (i == 5) { Breaks.break() } println(i) }) } println("break") }
执行结果：
1
2
3
4
6
7
8
9
10
break
def break() { Breaks.breakable({ for (i <- 1 to 10) { if (i == 5) { Breaks.break() } println(i) } }) println("break") }
执行结果：
1
2
3
4
break
标签：lex 开发 number vector color break tuple try nts
原文地址：http://www.cnblogs.com/eryuan/p/7307997.html
