多个map合并,key相同时则value相加
val map1 = Map(1 -> 1, 2 -> 2)
val map2 = Map(1 -> 11, 3 -> 3)
val map3 = Map(1 -> 111, 3 -> 3)
val mapList = List(map1, map2, map3)
val merged = mapList.reduce((m1, m2) =>
m1 ++ m2.map { case (k, v) => k -> (v + m1.getOrElse(k, 0)) }
)
some notes on scala future, includes:
一些容易忘记的spring boot知识要点.
注意,.yaml和.yml文件没任何区别.
@SpringBootApplication
// <=等价=>
@Configuration
@ComponentScan
@EnableAutoConfiguration
Scala中很多使用if的地方都可以用match case来替换.常见的就是下面的这种写法:
val res = msg match {
case it if it.contains("H") => "Hello"
case _ => "Other"
}
//更常见的用法是去匹配参数的模式:
case class Player(name: String, score: Int)
def message(player: Player) = player match {
case Player(_, score) if score > 100000 =>
"Get a job, dude!"
case Player(name, _) =>
"Hey, $name, nice to see you again!"
}
def printMessage(player: Player) = println(message(player))
scala type class notes: 关于scala type class非常好的文章