模式匹配
Java：switch case 值 对一个值进行条件判断，返回针对不同的条件进行不同的处理
Scala：match case 值/类型/集合
基本语法：
变量 match {
case value1 => 代码1
case value2 => 代码2
.....
case _ => 代码N
}
object MatchApp extends App {
val names = Array("Akiho Yoshizawa", "YuiHatano", "Aoi Sola")
val name = names(Random.nextInt(names.length)) //随机取一个名字
name match {
case "Akiho Yoshizawa" => println("吉老师...")
case "YuiHatano" => println("波老师...")
case _ => println("真不知道你们在说什么...")
}
def judgeGrade(grade:String): Unit = {
grade match {
case "A" => println("Excellent...")
case "B" => println("Good...")
case "C" => println("Just so so...")
case _ => println("You need work harder...")
}
}
judgeGrade("A")
judgeGrade("C")
judgeGrade("D")
}
加条件进行匹配：
object MatchApp extends App {
def judgeGrade(name:String, grade:String): Unit = {
grade match {
case "A" => println("Excellent...")
case "B" => println("Good...")
case "C" => println("Just so so...")
case _ if(name == "lisi") => println(name + " , You are a good boy, but...") //这里右多了一层判断
case _ => println("You need work harder...")
}
}
judgeGrade("zhangsan", "D")
judgeGrade("lisi", "D") //双重过滤
}
Array模式匹配：
object MatchApp extends App {
def greeting(array:Array[String]): Unit = {
array match {
case Array("zhangsan") => println("Hi:zhangsan")
case Array(x,y) => println("Hi: " + x + " , " + y)
case Array("zhangsan", _*) => println("Hi:zhangsan and other friends...") //zhangsan开头的任意个的一个数组。
case _ => println("Hi: everybody...")
}
}
greeting(Array("zhangsan")) //走第一个case
greeting(Array("lisi", "wangwu")) //走第二个case
greeting(Array("zhangsan","lisi", "wangwu")) //走第三个case
greeting(Array("lisi", "zhangsan", "wangwu")) //走第四个case
}
List模式匹配：
object MatchApp extends App {
def greeting(list:List[String]): Unit = {
list match {
case "zhangsan" :: Nil => println("Hi:zhangsan")
case x::y::Nil => println("Hi:" + x + " , " + y)
case "zhangsan" :: tail => println("Hi: zhangsan and other friends...")
case _ => println("Hi:everybody...")
}
}
greeting(List("zhangsan")) //走的第一个case
greeting(List("lisi", "zhangsan")) //走的第二个case
greeting(List("zhangsan","lisi")) //走的第二个case，先匹配上这个了。因为顺序的问题，所以没有做第三个case，而是走了第二个case。
greeting(List("PK","zhangsan","lisi")) //走的第四个case
}
类型匹配：Scala能根据类型做匹配
object MatchApp extends App {
def matchType(obj:Any): Unit = {
obj match {
case x:Int => println("Int")
case s:String => println("String")
case m:Map[_,_] => m.foreach(println)
case _ => println("other type")
}
}
matchType(1) //Int， 走的第一个case
matchType("1") //String，走的第二个case
matchType(1f) //other type ，走的第四个case
matchType(Map("name" -> "PK")) //(name,PK), 走的第三个case
}
Scala异常处理：
object ExceptionApp extends App {
//IO
val file = "test.txt"
try{
// open file
// use file
val i = 10/0 //是会报错的，不能被0除，需要用try catch。
println(i)
} catch {
case e:ArithmeticException => println("除数不能为0..")
case e:Exception => println(e.getMessage)
} finally {
//释放资源，一定能执行: close file
}
}
这就是我们常用的一个处理步骤，把要处理的东西丢到try里面，然后在catch里面通过 case 这种方式把我们的异常给捕获到，该怎么处理就是业务逻辑层面的问题了。最后把释放资源写到finally就行了。
case class模式匹配： case class不用new的，直接就能使用。
object CaseClassApp extends App {
def caseclassMatch(person:Person): Unit = {
person match {
case CTO(name,floor) => println("CTO name is: " + name + " , floor is : " + floor)
case Employee(name,floor) => println("Employee name is: " + name + " , floor is : " + floor)
case _ => println("other")
}
}
class Person
case class CTO(name:String, floor:String) extends Person
case class Employee(name:String, floor:String) extend Person
case class Other(name:String) extend Person
caseclassMatch(CTO("PK", "22"))
caseclassMatch(Employee("zhangsan", "2"))
caseclassMatch(Other("other"))
}
Some、None 模式匹配：
object CaseClassApp extends App {
val grades = Map("PK"->"A", "zhangsan"->"C")
def getGrade(name:String): Unit = {
val grade = grades.get(name)
grade match {
case Some(grade) => println(name + ": your grade is :" + grade)
case None => println("sorry....")
}
}
getGrade("zhangsan") //zhangsan: your grade is : C
getGrade("PK") //PK: your grade is : A
getGrade("lisi") //sorry....
}