声明一个变量
声明一个常量
显式指定类型
定义一个main函数
package org.admln.scalaclass HelloScala {}object HelloScala { def main (args: Array[String]) { println("hello scala") }} 定义一个普通函数
package org.admln.scalaclass HelloScala {}object HelloScala { def main (args: Array[String]) { println(hello("scala")) } def hello(name : String) : String = { "hello " + name }} 函数不带参数时可以省略括号
package org.admln.scalaclass HelloScala {}object HelloScala { def main (args: Array[String]) { println(hello()) } def hello() : String = { "hello scala" }} 定义一个匿名函数
package org.admln.scalaclass HelloScala {}object HelloScala { def main (args: Array[String]) { println(add(1,3)) } def add = (x : Int,y : Int) => x + y} 把函数赋给一个常量
package org.admln.scalaclass HelloScala {}object HelloScala { def main (args: Array[String]) { println(add(1,3)) } val add = (x : Int,y : Int) => x + y} 柯里化
package org.admln.scalaclass HelloScala {}object HelloScala { def main (args: Array[String]) { println(add(1)(2)) } def add(x : Int)(y : Int) = x + y} 可变参数
package org.admln.scalaclass HelloScala {}object HelloScala { def main (args: Array[String]) { println(variable("hello","admln")) } def variable(s : String*) = { s.foreach(x => println(x)) }} 参数默认值
package org.admln.scalaclass HelloScala {}object HelloScala { def main (args: Array[String]) { println(theDefault()) println(theDefault("scala")) } def theDefault(s : String="admln") : String= { "hello " + s }} package org.admln.scalaclass HelloScala {}object HelloScala { def main (args: Array[String]) { val num = 5; val result = if(num > 0) 1 else 0 println(result) }} while循环表达式
package org.admln.scalaclass HelloScala {}object HelloScala { def main (args: Array[String]) { var (n,r) = (10,0) while(n>0) { r = r + n n = n - 1 } println(r) }} for循环表达式
package org.admln.scalaclass HelloScala {}object HelloScala { def main (args: Array[String]) { //1<=10 for(i <- 1 to 10) { println(i) } //1<10 for(i <- 1 until 10) { println(i) } //只输出偶数 for(i <- 1 to 10 if i % 2 == 0 ) { println(i) } }} 创建一个类
package org.admln.scalaclass HelloScala {}class Person { var name : String = _ val age = 24}object MyPerson { def main(args: Array[String]) { val p = new Person p.name = "admln" println(p.name + " " + p.age) }} 使用私有属性（外部不能访问）
package org.admln.scalaclass HelloScala {}class Person { var name : String = _ val age = 24 private[this] val gender = "male"}object MyPerson { def main(args: Array[String]) { val p = new Person p.name = "admln" println(p.name + " " + p.age) }} 构造器
package org.admln.scalaclass HelloScala {}class Person(var name : String,val age : Int){ println("main constructor") var gender : String = _ def this(name : String,age : Int,gender : String) { this(name,age) this.gender = gender }}object MyPerson { def main(args: Array[String]) { val p = new Person("admln",24,"male") println(p.name + " " + p.age) }} package org.admln.scalaclass HelloScala {}class Person(var name : String,val age : Int){ println("main constructor") var gender : String = _ def this(name : String,age : Int,gender : String) { this(name,age) this.gender = gender }}class Student(name : String,age : Int,val major : String) extends Person(name,age) { println("subclass is person,major is" + major)}object MyPerson { def main(args: Array[String]) { val s = new Student("admln",24,"spark") }} 覆写父类的方法和字段
package org.admln.scalaclass HelloScala {}class Person(var name : String,val age : Int){ println("main constructor") var gender : String = "mail" def this(name : String,age : Int,gender : String) { this(name,age) this.gender = gender } val school = "usa"}class Student(name : String,age : Int,val major : String) extends Person(name,age) { println("subclass is person,major is" + major) override def toString = "override method" override val school = "china"}object MyPerson { def main(args: Array[String]) { val s = new Student("admln",24,"spark") println(s.toString) println(s.gender) }} 抽象类
package org.admln.scalaclass HelloScala {}abstract class Person { def speak var name : String val age : Int}class Worker extends Person { def speak { println("speak") } var name = "admln" val age = 24}object HelloScala extends App { val worker = new Worker worker.speak println(worker.name + " " + worker.age)} trait
trait中可以带有实现的方法，也可以带有抽象方法，使用trait的方式是使用with混入类中
1 package org.admln.scala 2 3 class UseTrait { 4 5 } 6 trait Logger { 7 def log(msg : String) { 8 println("log: " + msg) 9 }10 }11 12 class ConcreteLogger extends Logger {13 def concreteLog {14 log("It's admln")15 }16 }17 18 object UseTrait {19 def main(args: Array[String]) {20 val logger = new ConcreteLogger21 logger.concreteLog22 }23 } 覆写父类的抽象方法（不用使用override关键字）
package org.admln.scalaclass UseTrait {}trait Logger { def log(msg : String)}trait ConcreteLogger extends Logger { def log(msg : String) { println("log: " + msg) } } class Test extends ConcreteLogger { def test { log("It's admln") } } object UseTrait { def main(args: Array[String]) { val test = new Test test.test } } 如果子trait覆写父trait已经实现的方法，就必须使用override关键字
package org.admln.scalaclass UseTrait {}trait Logger { def log(msg : String) { println("log: " + msg) }}trait ConcreteLogger extends Logger { override def log(msg : String) { println(" child log: " + msg) }}class Test extends ConcreteLogger { def test { log("It's admln") }}object UseTrait { def main(args: Array[String]) { val test = new Test test.test }} 在对象中混入trait
package org.admln.scalaclass UseTrait {}trait Logger { def log(msg : String) { println("log: " + msg) }}trait ConcreteLogger extends Logger { override def log(msg : String) { println(" child log: " + msg) }}class Test extends Logger{ def test { log("It's admln") }}object UseTrait { def main(args: Array[String]) { val test = new Test with ConcreteLogger test.test }} apply方法和静态方法
package org.admln.scalaclass UsageOfApply {}class ApplyTest { def test { println("test") }}object ApplyTest { def apply() = new ApplyTest def staticTest { println("It's static method") }}object UsageOfApply { def main(args: Array[String]) { ApplyTest.staticTest val at = ApplyTest() at.test }} object 中的方法和属性都是静态的，所以是单例对象的理想载体
object本身就是一个单例对象函数式编程，把运算过程尽量写成一系列嵌套的函数调用
函数的定义
def 函数名称(变量名称 ： 变量类型) : 函数返回值类型 = { 函数体 }
如果函数仅包含一条语句，那么花括号可以选择不写
值函数
匿名函数
(参数名称 ： 参数类型) => 表达式
把匿名函数赋值给一个常量
闭包
代码与用到的非局部变量的混合
闭包 = 代码 + 非局部变量
高阶函数map函数
下划线代表数组中的每一个元素
高阶函数filter函数
高阶函数reduce函数
scala中的集合：List、Set、Tuple、Map
它们内部都是以apply方式来完成实例化的
List和Set
和java中的Set一样，里面不会存在相同元素
Tuple
下标从1开始
Map
Option
Option代表一个可有可无的值，有两个子类：Some和None
zip操作
partition操作
flatten操作
flatmap操作：map和flatten的结合
