1.简化代码
package com.scala.first import java.io.File
import javax.management.Query /**
* Created by common on 17-4-5.
*/
object FileMatcher { def main(args: Array[String]) { for (file <- filesHere)
println(file) println() for (file <- filesMatching("src", _.endsWith(_)))
println(file) for (file <- filesEnding("src"))
println(file) } private def filesHere = (new File(".")).listFiles //matcher是传入一个函数，返回boolean值，比如_.endsWith(_)
private def filesMatching(query: String, matcher: (String, String) => Boolean) = {
for (file <- filesHere; if matcher(file.getName, query)) yield file
} //上面的函数不够简洁，下面是更加简洁的定义
private def filesMatch(matcher: String => Boolean) = {
for (file <- filesHere; if matcher(file.getName)) yield file
} //然后可以定义使用不同matcher()的方法
def filesEnding(query: String) = {
filesMatch(_.endsWith(query))
} //使用exists来简化代码
def containsOdd(nums: List[Int]): Boolean = {
nums.exists(_ % 2 == 1)
} def containsNeg(nums: List[Int]): Boolean = {
nums.exists(_ < 0)
} }
输出是
./.idea
./build.sbt
./target
./input
./project
./src ./src
./src
2.柯里化
//柯里化，可以看成是两个函数,y是第一个函数sum(x: Int)的参数
def sum(x: Int)(y: Int) = {
x + y
} //println(sum2(2))的输出是4
def sum2 = sum(2)_
3.继承
package com.scala.first /**
* Created by common on 17-4-16.
*/
object AbstractClass { def main(args: Array[String]): Unit = {
val ae = new ArrayElement(Array("hello", "world"))
println(ae.width) val list1 = List(1,2,3,4)
val list2 = List(1,2,3,4,5)
//Scala中同时遍历两个list，如果长度不一样会截去
for((line1,line2) <- list1 zip list2){
println(line1+line2)
}
} } //定义一个抽象类
abstract class Element { //定义无参方法,抽象成员
def contents: Array[String] def height: Int = contents.length def width: Int = if (height == 0) 0 else contents(0).length } //扩展类，继承了上面的抽象类，需要实现抽象类中的方法
class ArrayElement(content: Array[String]) extends Element {
def contents: Array[String] = content
} //更加简洁的写法，contents和Element中的contents保持一致
class ArrayElement2(val contents: Array[String]) extends Element //另一个例子
class cat {
//确保一个成员不被子类重写，需要把其定义成final
// final val dangerous = false
val dangerous = false
} class tiger(override val dangerous: Boolean, private var age: Int) extends cat
4.特质
package com.scala.first /**
* Created by common on 17-4-17.
*/
object Trait { def main(args: Array[String]): Unit = {
val person = new Person //变量an可以初始化为任何混入了特质的类的对象，person对象包含了Animal特质
val an: Animal = person
println(an.toString) val p = new PP()
//输出People特质中的内容
p.say() } } trait Animal { def run(): Unit = {
println("Animal can run")
}
} //具有特质Animal
class Person extends Animal {
override def toString = "can say"
} //具有特质Animal
class Tiger extends Animal {
override def toString = "can run fast"
} //一个类只能继承一个父类。但是能混入多个特质
//特征的作用：
//1.把胖接口转换成瘦接口
//2.为类提供可堆叠的改变
class Live trait HasLeg //注意不能给特质中传递任何的参数
class PersonTiger extends Live with Animal with HasLeg {
println("混入了多个特质")
} class P {
def say(): Unit = {
println("I am a people")
}
} //特质在抽象方法中的动态绑定
trait People extends P {
abstract override def say(): Unit = {
println("I am a trait people")
}
} class PP extends People{
//输出People特质中的内容
}