Scala语法基础
1、scala下载
下载安装包直接安装
2、配置环境变量
path里面添加$SCALA_HOME/bin
3、idea环境配置
直接安装scala插件
4、变量声明
val表示常量,大型系统设计开发时，通常将传递给其他模块的对象设计为不可变。var表示变量
val result = 1+1 存放计算结果
val result =2
val name:String =null
val name,name1:String=null
5、数值类型
Byte Short Integer Long Double Float String Char
6、操作符
跟java基本一致除了无++，--
7、函数调用
除了无参数是不用加括号，其余和java一样
apply函数，通常采用这个构造对象。String中采用apply求底层字符
8、循环
只有while循环和简单for循环
var n = 10 for(i<-1 to 10){println((i+1))}
多重for循环
for(i<-1 to 9;j<-1 to 9){
if(j==9){
println(i*j)
}else{
print(i*j+" ")
}
}
if守卫
for(i<-1 to 100 if i %2=0){
println(i)
}
for推导式，构造集合
for(i<-1 to 100){
yield i
}
9、函数,=号表示有返回值,无返回值的称为过程
def sayHello（name：String，age：Int）={
if(age > 18){
printf("Hi,%s,hi you are a boy",name)
age
}else{
printf("Hi,%s,hi you are a children",name)
age
}
}
def fab(n:Int):Int={ if(n<=0) 1 else fab(n-1)+fab(n-2) }
10、参数默认值,带名参数,未命名参数必须放左边
def sayHello(firstName:String,middleName:String=""){ print(firstName + " "+ middleName) }
sayHello("杨春",middleName="chun")
变长参数,展开range序列
def sum(nums:Int*)：Int={ var result = 0 for(n <- nums){ result +=n } result }
sum(1 to 5:_*)
def sum(nums:Int*)：Int={
if(nums.length==0) 0
else nums.head + sum(nums.tail:_*)
}
11、lazy,第一次试用变量时才会计算
lazy val line = fromFile("")
12、异常捕获
try{ throw new IllegaArgumentException("illegal argument") }catch(){ case _:IllegaArgumentException =>print("abc") }finally{ print("abc") }
13、数组
val a = new Array[String](10)
val a = Array("hello","world")
val a = Array("hello",30) 数组公共类型Any
可变数组
ArrayBuffer
val b = ArrayBuffer[Int]()
b +=1 添加元素
b +=(2,3,4,5) 添加多个元素
b++=Array(6,7,8,9,10)
b.trimEnd(5)从尾部截断几个
b.insert(5,6)指定位置插入
b.remove(1)
b.remove(1,3)指定位置移除几个元素
a.toBuffer
b.toArray
for(i<-0 until b.length)
println(b(i))
for(i<-0 until (b.length,2))
println(b(i))
for(i<-(0 until b.length).reverse)
println(b(i))
for( e<-b)
println(e)
val sum = a.sum
val max = a.max
a.mkString(",")逗号分隔
a.mkString("(",",",")")
val a = Array(1,2,3,4,5)
val a2 =for(e<-a) yield e*e
val b = new ArrayBuffer[Int]()
val b2 = for(e<-b) yield e*e
val b3 = for(e<-b if e%2=0) yield e*e
a.filter(_%2=0).map(2*_)
a.filter{_%2=0}.map{2*_}
算法题移除掉第一个负数以后的所有负数，移动n次元素
val a = new ArrayBuffer[Int]()
a+=(1,2,3,4,5,-1.-3,-5,-9)
var fundFirstNegative =false
var arrayLength = a.length
var index =0
while(index <arrayLength){
if(a(index) > =0){
index+=1
}
else{
if(!fundFirstNegative){
fundFirstNegative = true
index+=1
}else{
a.remove(index)
arrayLength -=1
}
}
}
性能优化后,只移动一次元素
var fundFirstNegative =false
val keepIndexes = for(i<-0 until a.length if !fundFirstNegative ||a[i]>=0) yield {
if(a[i]<0){
fundFirstNegative = true
i
}
}
for(i<-0 until keepIndexes.length){a(i)=a(keepIndexes(i))}
a.trimEnd(a.length-keepIndexes.length)
14、map与tuple
map默认不可变
val map = Map("Leo" -> 30,"Jack" -> 25,"Jen" -> 25)
val ages = scala.collection.mutable.Map("Leo" -> 30,"Jack" -> 25,"Jen" -> 25)
val map = Map(("Leo" ,30),("Jack" ,25),("Jen",25))
val ages = scala.collection.mutable.HashMap[String,Int]
ages("Leo") = 41
ages+=("yang"->31,"Tom"->34)
ages-=("yang"）
更新不可变map，生成一个新的map
val ages2 = ages +("yang"->31,"Tom",34)
map的遍历
for((key,value)<-ages) println(key+" "+value)
for(key<-ages.keySet) println(key)
for(value<-ages.values) println(value)
for((key,value)<-ages) yield(value,key)
sortMap,自动按key排序
val ages = scala.collection.mutable.SortedMap("Leo" -> 30,"Jack" -> 25,"Jen" -> 25)
LinkedMap，记住插入顺序
val ages = scala.collection.mutable.LinkedHashMap[String,Int]
ages("leo")=30
ages("alice")=15
ages("jen")=25
Map的元素类型
val t = ("leo",30)
t._1
val names = Array("leo","jack","mike")
val ages = Array(30,24,26)
val nameAges = names.zip(ages)
for((name,age)<-nameAges) println(name+":"+age)
var t2 =("leo",30,"yang")
14、面向对象
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-28 13:04 */ class HelloWorld { private var name ="yangchun" def sayHello(){println("Hello,"+name)} def getName = name } package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-28 13:05 */ object Test { def main(args: Array[String]): Unit = { var helloWorld = new HelloWorld helloWorld.sayHello() helloWorld.getName } }
定义为var的类变量是会自动生成setter和getter方法
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-28 13:05 */ object Test { def main(args: Array[String]): Unit = { var helloWorld = new HelloWorld helloWorld.sayHello() helloWorld.getName var student = new Student println(student.name) student.name = "jack" println(student.name) } }
自己定义getter和setter方法
class Student2 { private var myName ="yangchun" def name="your name is" +myName def name_=(newName:String): Unit ={ println("you can not edit your name") } }
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-28 13:30 */ class Student3 { private var myAge = 0 def age_=(newAge:Int): Unit ={ if(newAge>0){ myAge = newAge }else{ println("Illegal age") } } def age=myAge def older(s:Student3)={ myAge > s.age } }
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-28 13:05 */ object Test { def main(args: Array[String]): Unit = { var helloWorld = new HelloWorld helloWorld.sayHello() helloWorld.getName var student = new Student println(student.name) student.name = "jack" println(student.name) var student3 = new Student3 var student4 = new Student3 student3.age =25 println(student3.age) student4.age =40; println(student4.age) println(student3.older(student4)) } }
如果不希望类成员变量被其他对象访问
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-28 13:30 */ class Student3 { private[this] var myAge = 0 def age_=(newAge:Int): Unit ={ if(newAge>0){ myAge = newAge }else{ println("Illegal age") } } def age=myAge def older(s:Student3)={ myAge > s.age } }
java风格的getter和setter
package com.xiaofeiyang.test import scala.beans.BeanProperty /** * @author: yangchun * @description: * @date: Created in 2020-04-28 18:16 */ class Student4 { @BeanProperty var name:String =_ }
package com.xiaofeiyang.test import scala.beans.BeanProperty /** * @author: yangchun * @description: * @date: Created in 2020-04-28 18:20 */ class Student5(@BeanProperty var name:String)
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-28 13:05 */ object Test { def main(args: Array[String]): Unit = { var helloWorld = new HelloWorld helloWorld.sayHello() helloWorld.getName var student = new Student println(student.name) student.name = "jack" println(student.name) var student3 = new Student3 var student4 = new Student3 student3.age =25 println(student3.age) student4.age =40; println(student4.age) println(student3.older(student4)) var student6 = new Student4 println(student6.getName) } }
15、构造函数，要么互相调用要么调用默认构造造函数
辅助构造函数
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-28 18:24 */ class Student6 { private var name = "" private var age =0 def this(name:String){ this() this.name = name; } def this(name:String,age:Int){ this(name) this.age =age; } }
主构造函数
package com.xiaofeiyang.test
/**
* @author: yangchun
* @description:
* @date: Created in 2020-04-28 18:24
*/
class Student6(var name:String ="yangchun",var age:Int=12) {
def this(name:String){
this()
this.name = name;
}
}
15、内部类，每个对象的内部类都不是同一个内部类
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-28 13:05 */ object Test { def main(args: Array[String]): Unit = { val c1 = new Class val s1 = c1.getStudent("leo") c1.students+=s1 val c2 = new Class val s2 = c2.getStudent("leo") c2.students+=s2 // c1.students += s2编译不过 } }
package com.xiaofeiyang.test import scala.collection.mutable.ArrayBuffer /** * @author: yangchun * @description: * @date: Created in 2020-04-28 18:36 */ class Class { class Student(val name:String){ } val students = new ArrayBuffer[Student] def getStudent(name:String)={ new Student(name) } }
16、object,单个实例，通常在里面放一些静态的field或者method。通常作为单例模式的实现和类的静态成员变量，比如工具方法。
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 7:06 */ object Person { private var eyeNum = 2 println("this person object!") def getEyeNum = eyeNum }
17、伴生对象，class和object同名，互相可以访问private变量
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 7:14 */ class Person2(val name:String,val age:Int) { def sayHello = println("Hi,"+name+",I know you are"+age+" years old"+",and usually you must have "+ Person2.eyeNum +" eyes") } object Person2{ private val eyeNum =2 def getEyeNum = eyeNum }
18、oject继承抽象类
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 7:24 */ abstract class Person3(var message:String){ def sayHello(name:String):Unit } object Person3 extends Person3("yangchun"){ override def sayHello(name: String): Unit = { println("name:"+name) } }
19、apply方法
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 7:27 */ class Person4(val name:String) { } object Person4{ def apply(name: String): Person4 = new Person4(name) } var person = Person4("leo")
20、主函数第二种写法
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 7:34 */ object Test2 extends App { if(args.length>0) println("Hello "+args(0)) else println("Hell World") }
21、枚举
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 7:38 */ object Season extends Enumeration { val SPRING,SUMMER,AUTUMN,WINTER = Value } package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 7:40 */ object Season2 extends Enumeration { val SPRING = Value(0,"spring") val SUMMER = Value(1,"summer") val AUTUMN = Value(2,"autumn") val WINTER = Value(3,"WINTER") } package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 7:34 */ object Test2 extends App { if(args.length>0) println("Hello "+args(0)) else println("Hell World") println(Season(1)) println(Season2.withName("spring")) for(ele<-Season2.values) println(ele) }
22、继承
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 11:09 */ class Person5 { private var name = "leo" def getName = name } package com.xiaofeiyang.test class Student7 extends Person5{ private var score = "A" def getScore = score }
package com.xiaofeiyang.test
class Student7 extends Person5{
private var score = "A"
def getScore = score
override def getName: String = "hi,"+super.getName
}
覆盖属性
package com.xiaofeiyang.test class Student7 extends Person5{ private var score = "A" def getScore = score override var name:String="leo" override def getName: String = "hi,"+super.getName }
23 isInstanceOf 和 asInstanceOf,类型判断和转换
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-28 13:05 */ object Test { def main(args: Array[String]): Unit = { val person = new Person5 val student = new Student7 println(student.getScore) println(student.getName) var s:Student7 =null if(student.isInstanceOf[Student7]) s= student.asInstanceOf[Student7] } }
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-28 13:05 */ object Test { def main(args: Array[String]): Unit = { val person = new Person5 val student = new Student7 println(student.getScore) println(student.getName) var s:Student7 =null if(student.isInstanceOf[Student7]) s= student.asInstanceOf[Student7] println(student.getClass == classOf[Person5]) } }
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-28 13:05 */ object Test { def main(args: Array[String]): Unit = { val person = new Person5 val student = new Student7 println(student.getScore) println(student.getName) var s:Student7 =null if(student.isInstanceOf[Student7]) s= student.asInstanceOf[Student7] println(student.getClass == classOf[Person5]) student match { case person5: Person5 =>println("it's Person's object") case _ =>println("unknown type") } } }
24 protected关键字来修饰field和method，子类可以直接访问，protectedthis只有自己子类对象才可以访问
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 13:35 */ class Person6 { protected var name ="leo" protected var age =30 } class Student8 extends Person6{ def sayHello = println("hello:"+name) def makeFriends(s:Student8): Unit ={ println("my age is"+age) //println("your age is"+s.age),编译不过 } }
25、主构造函数
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 13:45 */ class Animal(val name:String,val age:Int) { } class Dog(name:String,age:Int,var score:Double) extends Animal(name,age){ def this(name:String){ this(name,0,0) } def this(age:Int){ this("leo",age,0) } }
26、匿名内部类
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 13:56 */ class Person7(protected val name:String) { def sayHello ="Hello,I'm "+name }
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-28 13:05 */ object Test { def main(args: Array[String]): Unit = { val p = new Person7("leo"){ override def sayHello = "I,am "+name } } }
27、抽象类抽象字段
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 14:06 */ abstract class Animal2 { val name:String } class Dog2 extends Animal2{ val name:String ="gou2" }
28、trait作为接口使用
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 15:27 */ trait MakeFriendsTrait { def makeFriendsTrait(p:Person) } trait HelloTrait { def sayHello(name:String) } class Person(val name:String) extends MakeFriendsTrait with HelloTrait { override def makeFriendsTrait(p: Person): Unit = println("hello,"+p.name) override def sayHello(name: String): Unit = println("hello,my name is "+name) }
trait存放具体方法实现
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 15:27 */ trait MakeFriendsTrait { def makeFriendsTrait(p:Person) } trait HelloTrait { def sayHello(name:String) } trait logger{ def info(message:String)=println("log is："+message) } class Person(val name:String) extends MakeFriendsTrait with HelloTrait with logger { override def makeFriendsTrait(p: Person): Unit = println("hello,"+p.name) override def sayHello(name: String){ println("hello,my name is "+name) info(name) } }
trait定义field和继承父类field不一样
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 15:27 */ trait MakeFriendsTrait { def makeFriendsTrait(p:Person) } trait HelloTrait { def sayHello(name:String) } trait logger{ def info(message:String)=println("log is："+message) } trait eye{ val eyeNum:Int=2 } class Person(val name:String) extends MakeFriendsTrait with HelloTrait with logger with eye{ override def makeFriendsTrait(p: Person): Unit = println("hello,"+p.name) override def sayHello(name: String){ println("hello,my name is "+name) info(name) } def calcEyeNum(){ println(eyeNum) } }
给类混入trait
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:06 */ trait MyLogger extends Logged{ override def log(msg: String)= println(msg) } class MyLoggerImpl(val name:String) extends Logged { def sayHello: Unit ={ println("Hi,I'm "+name) log(name) } } trait Logged{ def log(msg:String){} }
trait调用链
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:20 */ trait Handler { def handle(msg:String){ } } trait DataValidHandler extends Handler { override def handle(msg: String){ println("check msg") super.handle(msg) } } trait Signature extends Handler { override def handle(msg: String){ println("signature msg") super.handle(msg) } } class HandlerImpl extends Signature with DataValidHandler { def sayHello(name:String): Unit ={ println("hello:"+name) handle(name) } }
Hi,I'm yangchun
yangchun
hello:yangchun
check msg
signature msg
Process finished with exit code 0
trait具体方法和抽象方法混合使用
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:31 */ trait Valid { def getName:String def valid:Boolean=getName=="leo" } class ValidImpl(val name:String) extends Valid{ println(valid) override def getName=name }
trait构造代码，不在任何方法里面的代码就是构造函数。从左到右一直调用
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:06 */ trait MyLogger extends Logged{ println("MyLogger construct") } trait TimeLogger extends Logged{ println("TimeLogger construct") } class MyLoggerImpl() extends MyLoggerImplFather with MyLogger with TimeLogger { println("myLoggerImpl construct") } trait Logged{ println("logged construct") } class MyLoggerImplFather{ println("myloggerImplFather construct") }
myloggerImplFather construct
logged construct
MyLogger construct
TimeLogger construct
myLoggerImpl construct
trait field的初始化
会报空指针异常
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 17:33 */ trait TraitField { val msg:String println("msg:"+msg.toString) } class TraitTest extends TraitField{ val msg: String = "init" }
提前混入一个msg
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:13 */ object Test{ def main(args: Array[String]): Unit = { val TraitTest = new {override val msg:String="tiqian"} with TraitTest with TraitField } }
定义的时候混入一个
trait TraitField { val msg:String println("msg:"+msg.toString) } class TraitTest extends { val msg: String = "init" } with TraitField
使用lazy
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 17:33 */ trait TraitField { lazy val msg:String = null println("msg:"+msg.toString) } class TraitTest extends TraitField { override lazy val msg: String = "init" }
28、trait继承class
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 17:44 */ class MyUtil{ def printMessage(msg:String)=println("msg:"+msg) } trait HeritUtil extends MyUtil{ def log(msg:String)=printMessage(msg) } class TraitHeritClass(val msg:String)extends HeritUtil { def sayHello: Unit ={ log("hi,this is"+msg) printMessage("hi,myUtil is"+msg) } }
29、Scala函数编程，独立定义函数
def sayHello(name:String)=println("hello:"+name)
var sayHelloFunc = sayHello _
sayHelloFunc("leo")
匿名函数
var sayHiFunc = (name:String)=>println("hi:"+name)
sayHiFunc("leo")
高阶函数就是将函数作为返回值
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:13 */ object Test{ def main(args: Array[String]): Unit = { val traitHeritClass = new TraitHeritClass("yangchu") traitHeritClass.sayHello def sayHello(name:String)=println("hello:"+name) var sayHelloFunc = sayHello _ sayHelloFunc("leo") var sayHiFunc = (name:String)=>println("hi:"+name) sayHiFunc("leo") def greeting(func:(String)=>Unit,name:String){func(name)} greeting(sayHelloFunc,"yangchun") greeting(sayHiFunc,"lidan") } }
Array(1,2,3,4,5).map((num:Int)=>num*num)
高阶函数返回一个匿名函数
def getGreetingFunc(msg:String)=(name:String)=>println(msg+","+name) val greetingHello = getGreetingFunc("Hello") val greetingHi = getGreetingFunc("Hi") greetingHello("leo") greetingHi("leo")
高阶函数可以自动推断参数类型
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:13 */ object Test{ def main(args: Array[String]): Unit = { val traitHeritClass = new TraitHeritClass("yangchu") traitHeritClass.sayHello def sayHello(name:String)=println("hello:"+name) var sayHelloFunc = sayHello _ sayHelloFunc("leo") var sayHiFunc = (name:String)=>println("hi:"+name) sayHiFunc("leo") def greeting(func:(String)=>Unit,name:String){func(name)} greeting(sayHelloFunc,"yangchun") greeting(sayHiFunc,"lidan") Array(1,2,3,4,5).map((num:Int)=>num*num) def getGreetingFunc(msg:String)=(name:String)=>println(msg+","+name) val greetingHello = getGreetingFunc("Hello") val greetingHi = getGreetingFunc("Hi") greetingHello("leo") greetingHi("leo") greeting((name)=>println("haha"+name),"yangchun") greeting(name=>println("haha"+name),"yangchun") } }
def triple(func:(Int)=>Int)={func(3)}
println(triple(3*_))
println(Array(1,2,3,4,5).map(2*_))
(1 to 9 ).map("*" * _).foreach(println _)
(1 to 9 ).map("*" * _).foreach(println _)
(1 to 20).filter(_ %2==0)
(1 to 9 ).reduceLeft(_*_)
Array(1,2,3,4,5).sortWith(_ < _)
30、闭包，函数在变量不属于其作用域范围时，还能对其进行访问。msg作为函数的局部变量，在getGreetingFunc执行完成后，还存在创建的函数中，调用时值为hello的msg被保留在函数体内部，可以反复使用
def getGreetingFunc(msg:String)=(name:String)=>println(msg+","+name) val greetingHello = getGreetingFunc("Hello") val greetingHi = getGreetingFunc("Hi") greetingHello("leo") greetingHi("leo")
31、SAM 转换，匿名函数转换成类
package com.xiaofeiyang.test import java.awt.event.{ActionEvent, ActionListener} import javax.swing.JButton /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:13 */ object Test{ def main(args: Array[String]): Unit = { val button = new JButton() button.addActionListener(new ActionListener { override def actionPerformed(e: ActionEvent): Unit = println("click me") }) implicit def getActionListener(actionProcFunc:(ActionEvent=>Unit))=new ActionListener { override def actionPerformed(e: ActionEvent) {actionProcFunc(e)} } button.addActionListener((event:ActionEvent)=>println("click me")) } }
32、Currying函数
package com.xiaofeiyang.test import java.awt.event.{ActionEvent, ActionListener} import javax.swing.JButton /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:13 */ object Test{ def main(args: Array[String]): Unit = { def sum(a:Int,b:Int) = a+b def sum2(a:Int) = (b:Int)=>a+b def sum3(a:Int)(b:Int)=a+b } }
33、return在匿名函数里面返回值，作为带名函数的返回值
package com.xiaofeiyang.test import java.awt.event.{ActionEvent, ActionListener} import javax.swing.JButton /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:13 */ object Test{ def main(args: Array[String]): Unit = { def greeting(name:String)={ def sayHello(name:String):String={ return "Hello:"+name } sayHello("yangchun") } } }
34、集合操作
Iterable，Seq，Set，Map，Iterable是所有trait的根trait。集合分为可变不可变，mutable和unmutable。Seq是所有range，array，list，ArrayBuffer的根trait
list
package com.xiaofeiyang.test import java.awt.event.{ActionEvent, ActionListener} import javax.swing.JButton /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:13 */ object Test{ def main(args: Array[String]): Unit = { val list = List(1,2,3,4,5)//不可变 println(list.head) println(list.tail)//不包含第一个元素 val list2 = -1::list//合并 def decorator(I:List[Int],prefix:String): Unit ={ if(I!=Nil){ println(prefix+I.head) decorator(I.tail,prefix) } } decorator(list,"*") } }
LinkedHashSet
package com.xiaofeiyang.test
import scala.collection.mutable
/**
* @author: yangchun
* @description:
* @date: Created in 2020-04-29 16:13
*/
object Test{
def main(args: Array[String]): Unit = {
var set = mutable.LinkedHashSet(1,2,3,4)
set+=5
set.foreach(println(_))
var set2 = mutable.SortedSet(2,3,4,1)
set2.foreach(println(_))
}
}
函数式编程
var list = List("aiden yang","orion liu","horny guan").flatMap(_.split(" "))
list.map(println(_))
var list2 = List("aiden yang","orion liu","horny guan").map("my name is"+_)
list2.map(println(_))
var list3 = List("aiden yang","orion liu","horny guan").zip(List(100,60,70))
list3.map(println(_))
小案例单词数量统计
var file1 = scala.io.Source.fromFile("d://tes1.txt").mkString
var file2 = scala.io.Source.fromFile("d://tes2.txt").mkString
val lines = List(file1,file2)
println(lines.flatMap(_.split(" ")).map((_,1)).map(_._2).reduceLeft(_ + _))
35、模式匹配
可以匹配值，可以匹配类型，有没有值匹配
基础语法
package com.xiaofeiyang.test import scala.collection.mutable /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:13 */ object Test{ def main(args: Array[String]): Unit = { def judgeGrade(score:String): Unit ={ score match { case "A" =>println("Excellent") case "B" =>println("Good") case "C" =>println("Just so so") case _ =>println("you need to work harder") } } judgeGrade("A") } }
升级版本，if守卫
package com.xiaofeiyang.test import scala.collection.mutable /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:13 */ object Test{ def main(args: Array[String]): Unit = { def judgeGrade(name:String,score:String): Unit ={ score match { case "A" =>println("Excellent") case "B" =>println("Good") case "C" =>println("Just so so") case _ if name =="leo"=>println(name+"you are a good boy, come on") case _ =>println("you need to work harder") } } judgeGrade("A","yangchun") } }
package com.xiaofeiyang.test import scala.collection.mutable /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:13 */ object Test{ def main(args: Array[String]): Unit = { def judgeGrade(name:String,score:String): Unit ={ score match { case "A" =>println("Excellent") case "B" =>println("Good") case "C" =>println("Just so so") case _grade if name =="leo"=>println(name+"you are a good boy, you grade is"+_grade) case _ =>println("you need to work harder") } } judgeGrade("leo","F") } }
类型匹配，异常处理
package com.xiaofeiyang.test import java.io.{FileNotFoundException, IOException} import scala.collection.mutable /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:13 */ object Test{ def main(args: Array[String]): Unit = { def processException(e:Exception): Unit ={ e match { case e1:IllegalArgumentException=>println("you have illegal arguments! exception is:"+e) case e2:FileNotFoundException=>println("file not found") case e3:IOException=>println("io error") case _:Exception=>println("unknown exception") } } processException(new IOException()) } }
Array和List的元素进行匹配
package com.xiaofeiyang.test import java.io.{FileNotFoundException, IOException} import scala.collection.mutable /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:13 */ object Test{ def main(args: Array[String]): Unit = { def greeting(arr:Array[String]): Unit ={ arr match { case Array("leo")=>println("hi,leo") case Array(girl1,girl2,girl3)=>println("hi,girl i know your name"+girl1+","+girl2+","+girl3) case Array("leo",_*)=>println("hi,leo,please introduce your friends to me") case stranger=>println("who are you") } } greeting(Array("leo")) greeting(Array("yanchun","lidan","yanghuan")) greeting(Array("leo","lidan","yanghuan","zhangwei")) greeting(Array("zhangjiayao")) def greeting2(arr:List[String]): Unit ={ arr match { case "leo"::Nil=>println("hi,leo") case girl1::girl2::girl3=>println("hi,girl i know your name"+girl1+","+girl2+","+girl3) case "leo"::tail=>println("hi,leo,please introduce your friends to me") case _=>println("who are you") } } greeting2(List("leo")) greeting2(List("yanchun","lidan","yanghuan")) greeting2(List("leo","lidan","yanghuan","zhangwei")) greeting2(List("zhangjiayao")) } }
case class和模式匹配，case class会自动生成getter和setter方法，自动定义伴生对象和apply方法
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:13 */ object Test{ def main(args: Array[String]): Unit = { def judgeIdentify(p:person){ p match { case teacher(name,subject)=>println("teacher,name is"+name+",subject is"+subject) case student(name,classroom)=>println("student,name is"+name+",classroom is"+classroom) case _=>println("illegal access ,please go out of the school") } } val leo:person = teacher("leo","english") judgeIdentify(leo) } } class person case class student(name:String,classroom:String) extends person case class teacher(name:String,subject:String) extends person
Option与模式匹配 Some表示有值，None表示没有值
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:13 */ object Test{ def main(args: Array[String]): Unit = { val grades = Map("leo"->23,"jack"->25) def getGrade(name:String)={ val grade = grades.get(name) grade match { case Some(grade)=>println(grade) case None=>println("none") } } getGrade("leo") } }
36、类型参数相当于泛型，就是类型参数，用来限制集合里面的类型
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:13 */ object Test{ def main(args: Array[String]): Unit = { var leo = new student[Int](1) leo.getSchoolId(2) } } class student[T](val localId:T){ def getSchoolId(hukould:T)="S-"+hukould+"-"+localId }
泛型函数
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:13 */ object Test{ def main(args: Array[String]): Unit = { var leo = new student[Int](1) leo.getSchoolId(2) def getCard[T](content:T)={ if(content.isInstanceOf[Int])"card:001,"+content else if(content.isInstanceOf[String])"card:this is your card,"+content else "card:"+content } getCard[String]("hello") getCard[Int](100) } } class student[T](val localId:T){ def getSchoolId(hukould:T)="S-"+hukould+"-"+localId }
上边界，指定传入参数必须是某个类的子类
package com.xiaofeiyang.test
/**
* @author: yangchun
* @description:
* @date: Created in 2020-04-29 16:13
*/
object Test{
def main(args: Array[String]): Unit = {
def getIDCard[T >: Child](p1: T) {
if(p1.getClass==classOf[Child]) println("please tell your parents")
else if(p1.getClass==classOf[Father]) println("please sign your name")
else println("sorry,you are not allowed to get id card")
}
val child = new Child("leo")
val father = new Father("jack")
getIDCard[Child](child)
getIDCard[Father](father)
val work = new work
getIDCard(work)
}
}
class work
class Father(val name:String)
class Child(name:String)extends Father(name){
}
view bounds就是上下边界加强版本，支持对隐式类型进行转换，再判断是否在边界内
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:13 */ object Test { def main(args: Array[String]): Unit = { var leo = new Student("leo") var jack = new Student("jack") var party1 = new Party(leo,jack) party1.pay() var doggy = new Dog("doggy") var party = new Party(leo,doggy) party.pay() } implicit def dog2Person(dog: Object): Person = { if(dog.isInstanceOf[Dog]) { val _dog = dog.asInstanceOf[Dog]; new Person(_dog.name) } else if(dog.isInstanceOf[Person]){ dog.asInstanceOf[Person] }else { Nil } } } class Person(val name:String){ def sayHello = println("Hello,I'm"+name) def makeFriends(p:Person): Unit ={ sayHello p.sayHello } } class Student(name:String) extends Person(name) class Dog(val name:String){def sayHello=println("Wang,Wang,I'm "+name)} class Party[T <% Person](p1:T,p2:T){ def pay(): Unit ={ p2.makeFriends(p1) } }
context bounds,它基于全局上下文自动注入
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:13 */ object Test { def main(args: Array[String]): Unit = { val cal = new Calculator(1,2) println(cal.max) } } class Calculator[T:Ordering](val num1:T,val num2:T){ def max(implicit order:Ordering[T]) = if(order.compare(num1,num2)>0) num1 else num2 }
Manifest Context Bounds，实例化一个泛型数组
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:13 */ object Test { def main(args: Array[String]): Unit = { def packageFood[T:Manifest](food:T*)={ val foodPackage = new Array[T](food.length) for(i<-0 until food.length) foodPackage(i)= food(i) foodPackage } var yangpai = new Meat("yangpai") var gongbaojiding = new Meat("gongbaojiding") var qingcai = new Vegetable("qingcai") var meats = packageFood((yangpai,gongbaojiding)) meats.foreach(println(_.)) } } class Meat(val name:String) class Vegetable(val name:String)
协变和逆变，+T就是类及子类都可以，-T就是类和父类都可以
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:13 */ object Test { def main(args: Array[String]): Unit = { def enterMeet(card:Card[Master]){ println("master enter meet") } def enterMeet2(card1:Card[Professional]){ println("professional enter meet2") } var leo = new Card[Master]("leo") var jack = new Card[Professional]("jack") enterMeet(leo) enterMeet2(jack) enterMeet(jack) } } class Master class Professional extends Master class Card[+T](val name:String) class Card1[-T](val name:String)
37、隐式转换，一般会去源类型和目标类型以及伴生对象里面查找隐式转换函数，程序当前作用域，手动import导入隐式转换函数。发生时间调用函数参数类型不一致，调用方法不存在。调用方法有该方法但是
参数不匹配
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:13 */ object Test { def main(args: Array[String]): Unit = { var ticketNumber =0 def buySpecialTicket(p:SpecialPerson)={ ticketNumber +=1 "T-"+ticketNumber } println(buySpecialTicket(new Student("leo"))) println(buySpecialTicket(new Older("lidan"))) } implicit def object2SpecialPerson(obj:Object):SpecialPerson={ if(obj.getClass==classOf[Student]){ val stu = obj.asInstanceOf[Student] new SpecialPerson(stu.name) }else if(obj.getClass==classOf[Older]){ val older = obj.asInstanceOf[Older] new SpecialPerson(older.name) }else{ Nil } } } class SpecialPerson(val name:String) class Student(val name:String) class Older(val name:String)
增加类功能
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:13 */ object Test { def main(args: Array[String]): Unit = { var leo =new Man("leo") leo.emitLaser } implicit def man2Superman(man:Man):Superman={ new Superman(man.name) } } class Man(val name:String) class Superman(name:String) extends Man(name){ def emitLaser = println("emit a laser") }
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:13 */ object Test { def main(args: Array[String]): Unit = { var ticketHous = new TicketHous println(ticketHous.buySpecialTicket(new Student("leo"))) println(ticketHous.buySpecialTicket(new Older("lidan"))) } implicit def object2SpecialPerson(obj:Object):SpecialPerson={ if(obj.getClass==classOf[Student]){ val stu = obj.asInstanceOf[Student] new SpecialPerson(stu.name) }else if(obj.getClass==classOf[Older]){ val older = obj.asInstanceOf[Older] new SpecialPerson(older.name) }else{ Nil } } } class SpecialPerson(val name:String) class Student(val name:String) class Older(val name:String) class TicketHous(){ var ticketNumber =0 def buySpecialTicket(p:SpecialPerson)={ ticketNumber +=1 "T-"+ticketNumber } }
隐式参数
package com.xiaofeiyang.test /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:13 */ object Test { def main(args: Array[String]): Unit = { implicit val signPe = new SignPen def signForExam(name:String)(implicit signPen:SignPen)={ signPe.write(name+"welcome to exam") } signForExam("leo") } } class SignPen{ def write(content:String)=println(content) }
38、actor入门，相当于java的多线程
package com.xiaofeiyang.test import akka.actor.{Actor, ActorSystem, Props} /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:13 */ object Test { private val myActorFactory = ActorSystem("myActorFactory") private val helloActorRef = myActorFactory.actorOf(Props[HelloActor],"helloActor") def main(args: Array[String]): Unit = { helloActorRef ! "leo" } } class HelloActor extends Actor{ override def receive: Receive = { case name:String=>println("hello,"+name) } }
线程之间精准通讯
package com.xiaofeiyang.test import akka.actor.{Actor, ActorSystem, Props} /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:13 */ object Test { private val myActorFactory = ActorSystem("myActorFactory") private val helloActorRef = myActorFactory.actorOf(Props[UserManageActor],"helloActor") def main(args: Array[String]): Unit = { helloActorRef ! Register("leo","12345") helloActorRef ! Login("leo","12345") } } case class Login(username:String,password:String) case class Register(username:String,password:String) class UserManageActor extends Actor{ override def receive: Receive = { case Login(username,password)=>println("login,username "+username+" password "+password) case Register(username,password)=>println("register,username "+username+" password "+password) } }
package com.xiaofeiyang.test import akka.actor.{Actor, ActorRef, ActorSystem, Props} /** * @author: yangchun * @description: * @date: Created in 2020-04-29 16:13 */ object Test { private val myActorFactory = ActorSystem("myActorFactory") private val leoRef = myActorFactory.actorOf(Props[LeoTelePhoneActor],"leo") private val jackRef = myActorFactory.actorOf(Props[JackTelePhoneActor],"jack") def main(args: Array[String]): Unit = { leoRef ! Message("I'm free",jackRef) } } case class Message(content:String,sender:ActorRef) class LeoTelePhoneActor extends Actor{ override def receive: Receive = { case Message(content,sender)=>println("leo telephone:"+content); sender ! "I am leo,please call me later" } } class JackTelePhoneActor extends Actor{ override def receive: Receive = { case response:String=>println("jack telephone:"+response) } }
