for(i <- 1 to 9;j <- 1 to 9){
if(j==9){
println(i*j)
}else{
print(i*j+" ")
}
}
def sayHello(name:String,age: Int) = {
if(age > 19) {
printf("hi %s,you are a big boy\n",name)
age
}else{
printf("hi ,%s,you are a children\n",name)
age
}
}
def sum(n:Int) = {
var result = 0
for( i<- 1 to n){
result += i
}
result
}
def fab(n: Int): Int = {
if(n <= 0) 1
else fab(n-1)+fab(n-2)
}
def sayHello(firstName:String,middleName:String = "",lastName:String="") = firstName + " " +middleName+" "+lastName
sayHello(firstName="hahha",middleName="xxx",lastName="ggg")
def sum(nums: Int*)={
var result = 0
for(num <- nums){
result += num
}
result
}
sum(1 to 5: _*) //值为15,表示取出1到5的整数相加
def sum2(nums:Int*):Int = {
if(nums.length == 0) 0
else nums.head + sum2(nums.tail: _*)
}
//定义过程,不会有返回值
def sayHello(name:String):Unit = "Hello,"+name
lazy val lines = fromFile("/home/1.text").mkString
//使用的时候才会执行上面这句
print(lines)
异常
try{
throw new lllegAlrgumentException("x should not be negative")
}catch{
case_:lllegAlrgumentException => print("sorry,error")
}finally{
print("release io ")
}
scala> b.insert(1,2,2,3)
scala> b
res20: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1, 2, 2, 3, 2, 3, 5, 5, 6, 9, 8)
scala> b.insert(1,1,2,9)
scala> b
res22: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1, 1, 2, 9, 2, 2, 3, 2, 3, 5, 5, 6, 9, 8)
scala> b.insert(1,7,8)
scala> b
res24: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1, 7, 8, 1, 2, 9, 2, 2, 3, 2, 3, 5, 5, 6, 9, 8)
scala> b.remove(1)
res25: Int = 7
scala> b
res26: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1, 8, 1, 2, 9, 2, 2, 3, 2, 3, 5, 5, 6, 9, 8)
scala> b.remove(1,3)
scala> b
res29: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1, 9, 2, 2, 3, 2, 3, 5, 5, 6, 9, 8)
//互相转换
scala> b.toArray
res30: Array[Int] = Array(1, 9, 2, 2, 3, 2, 3, 5, 5, 6, 9, 8)
scala> b.toBuffer
res31: scala.collection.mutable.Buffer[Int] = ArrayBuffer(1, 9, 2, 2, 3, 2, 3, 5, 5, 6, 9, 8)
scala> for(i <- 0 until b.length) print(b(i))
192232355698
//跳跃遍历
scala> for(i <- 0 until (b.length,2)) print(b(i))
123359
//从尾部遍历
scala> for(i <- (0 until b.length).reverse) print(b(i))
896553232291
//增强for循环
scala> for(i <- b) print(i)
192232355698
scala> val b = Array(9,8,2,2,3,4)
b: Array[Int] = Array(9, 8, 2, 2, 3, 4)
scala> scala.util.Sorting.quickSort(b)
scala> b
res3: Array[Int] = Array(2, 2, 3, 4, 8, 9)
scala> b.mkString
res5: String = 223489
scala> b.mkString(",")
res6: String = 2,2,3,4,8,9
scala> b.toString
res7: String = [I@6d4502ca
scala> val a = Array(1,2,3,4,5)
a: Array[Int] = Array(1, 2, 3, 4, 5)
scala> val a2 = for(ele <- a) yield ele * ele
a2: Array[Int] = Array(1, 4, 9, 16, 25)
scala> val a3 = for(ele <- a if ele % 2==0) yield ele * ele
a3: Array[Int] = Array(4, 16)
scala> a.filter(_%2==0).map(_*2)
res8: Array[Int] = Array(4, 8)
scala> a.filter{_%2==0} map{_*2}
res9: Array[Int] = Array(4, 8)
scala> import scala.collection.mutable.ArrayBuffer
import scala.collection.mutable.ArrayBuffer
scala> val a = ArrayBuffer[Int]()
a: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer()
scala> a += (1,2,3,4,5,-1,-3,-5,-7)
res10: a.type = ArrayBuffer(1, 2, 3, 4, 5, -1, -3, -5, -7)
scala> :paste
// Entering paste mode (ctrl-D to finish)
var foundFirstNegative = false
var arrayLength = a.length
var index = 0
while(index < arrayLength){
if(a(index)>=0){
index+=1
}else{
if(!foundFirstNegative){foundFirstNegative = true;index+=1}
else{a.remove(index);arrayLength-=1}
}
}
// Exiting paste mode, now interpreting.
foundFirstNegative: Boolean = true
arrayLength: Int = 6
index: Int = 6
scala> a
res12: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1, 2, 3, 4, 5, -1)
第二种,性能更高,数组更少移动
var foundFirstNegative = false
val keepIndexes = for(i <- 0 until a.length if !foundFirstNegative || a(i)>=0
) yield{
if(a(i)<0) foundFirstNegative = true
i
}
for (i <- 0 until keepIndexes.length){a(i) = a(keepIndexes(i))}
a.trimEnd(a.length - keepIndexes.length)
scala> a
res15: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1, 2, 3, 4, 5, -1)
//不可变Map
scala> val ages = Map("Leo"->30,"den"->20,"jack"->23)
ages: scala.collection.immutable.Map[String,Int] = Map(Leo -> 30, den -> 20, jack -> 23)
scala> ages("Leo")
res0: Int = 30
scala> ages("Leo") = 20
<console>:13: error: value update is not a member of scala.collection.immutable.Map[String,Int]
ages("Leo") = 20
^
//可变Map
scala> val ages = scala.collection.mutable.M
Map MapBuilder MapLike MapProxy MultiMap MutableList
scala> val ages = scala.collection.mutable.Map("Leo"->30,"den"->20,"jack"->23)
ages: scala.collection.mutable.Map[String,Int] = Map(jack -> 23, den -> 20, Leo -> 30)
scala> ages("Leo")=24
scala> ages("Leo")
res3: Int = 24
//第三种创建方式
scala> val ages = Map(("Leo",30),("Jen",31),("jack",33))
ages: scala.collection.immutable.Map[String,Int] = Map(Leo -> 30, Jen -> 31, jack -> 33)
//第四种创建方式
scala> val ages = new scala.collection.mutable.HashMap[String,Int]
ages: scala.collection.mutable.HashMap[String,Int] = Map()
scala> ages.put("jack",24)
res5: Option[Int] = None
scala> ages
res6: scala.collection.mutable.HashMap[String,Int] = Map(jack -> 24)
//必须判断是否存在,否则不存在会报错
scala> val age = if(ages.contains("jack")) ages("jack") else 0
age: Int = 24
//或者取默认值
scala> val leoAge = ages.getOrElse("Leo",0)
leoAge: Int = 0
//一次性添加多个key-value对
scala> ages+=("Mike"->35,"Tom"->50)
res9: ages.type = Map(jack -> 24, Mike -> 35, Tom -> 50, Leo -> 30)
//移除元素
scala> ages-="Mike"
res10: ages.type = Map(jack -> 24, Tom -> 50, Leo -> 30)
//Map本身不可变,下列操作通过生成新的Map实现
scala> val aggs = Map("Leo"->24,"jike"->34)
aggs: scala.collection.immutable.Map[String,Int] = Map(Leo -> 24, jike -> 34)
scala> val ages2 = aggs + ("Mike"->20,"Tom"->70)
ages2: scala.collection.immutable.Map[String,Int] = Map(Leo -> 24, jike -> 34, Mike -> 20, Tom -> 70)
scala> val ages3 = aggs-"Leo"
ages3: scala.collection.immutable.Map[String,Int] = Map(jike -> 34)
scala> aggs
res12: scala.collection.immutable.Map[String,Int] = Map(Leo -> 24, jike -> 34)
//Map遍历
scala> for((key,value) <- ages) println(key +" "+value)
jack 24
Tom 50
Leo 30
scala> for(key <- ages.keySet)println(key)
jack
Tom
Leo
scala> for(value <- ages.values) println(value)
24
50
30
//反转key和value
scala> for((key,value) <- ages) yield(value,key)
res16: scala.collection.mutable.HashMap[Int,String] = Map(50 -> Tom, 30 -> Leo, 24 -> jack)
//自动对Map的key排序
scala> val ages = scala.collection.immutable.SortedMap("leo"->30,"alice"->14,"jen"->25)
ages: scala.collection.immutable.SortedMap[String,Int] = Map(alice -> 14, jen -> 25, leo -> 30)
//保证插入顺序和读取顺序相同
scala> val aggs = new scala.collection.mutable.LinkedHashMap[String,Int]
aggs: scala.collection.mutable.LinkedHashMap[String,Int] = Map()
scala> aggs("leo")=30
scala> aggs("jike")=40
scala> aggs("alice")=15
scala> aggs
res22: scala.collection.mutable.LinkedHashMap[String,Int] = Map(leo -> 30, jike -> 40, alice -> 15)
//简单tuple
scala> val t = ("leo",30)
t: (String, Int) = (leo,30)
scala> t._1
res23: String = leo
scala> t._2
res24: Int = 30
//zip操作,将两数组拼接成元组
scala> val names = Array("leo","jack","mike")
names: Array[String] = Array(leo, jack, mike)
scala> val ages = Array(30,24,26)
ages: Array[Int] = Array(30, 24, 26)
scala> val nameAges = names.zip(ages)
nameAges: Array[(String, Int)] = Array((leo,30), (jack,24), (mike,26))
scala> for((name,age)<-nameAges) println(name +":" + age)
leo:30
jack:24
mike:26