Scala入門筆記二

目錄使用反引號定義識別符號

無引數方法

優先順序規則

if語句

迴圈生成器表示式

保護式: 篩選元素

新增多個保護式

yielding

擴充套件作用域與值定義

while迴圈

do...while迴圈

條件操作符

使用try...catch...final子句

惰性賦值

列舉可插入字串

不能使用保留字.

val xyz_++= = 1

def `test that addition work`= assert(1 + 1 = 2)

list(1, 2, 3, 4).filter((i: int) => iseven(i)).foreach((i: int) => println(i))

list(1, 2, 3, 4).filter(i => iseven(i)).foreach(i => println(i))
list(1, 2, 3, 4).filter(iseven).foreach(println)
list(1, 2, 3, 4) filter iseven foreach println

1. 所有字母

2. |
3. ^
4. &
5. < >
6. = !
7. :
8. + -
9. * / %
10. 其他特殊字元

scala> val list = list('c', 'd')

list: list[char] = list(c, d)
scala> 'a' :: list
res1: list[char] = list(a, c, d)
scala> val list = list('c', 'd')
list: list[char] = list(c, d)
scala> 'b' :: list
res2: list[char] = list(b, c, d)
scala> list.::('a')
res3: list[char] = list(a, c, d)
scala> 'a' :: list
res4: list[char] = list(a, c, d)
scala> 'b' :: list
res5: list[char] = list(b, c, d)

scala不支援三元表示式

示例**

val list = list("a", "b", "c")

for (item <- list)
println(item)

a

bc

**

val list = list("abc", "cde", "efg")

for (item <- list
if item.contains("c")
)println(item)

abc

cde

示例

val list = list("abc", "bcd", "cde")

for (item <- list
if item.contains("b")
if !item.startswith("a")
)println(item)
for (item <- list
if item.contains("b") && !item.startswith("a")
)println(item)

bcd

bcd

**

val list = list("abc", "bcd", "cde")

val filteritems =  for  yield item
filteritems

scala> val list = list("abc", "bcd", "cde")

list: list[string] = list(abc, bcd, cde)
scala> val filteritems =  for  yield item
filteritems: list[string] = list(bcd)

**

val list = list("abc", "bcd", "cde")

val upcaseitems = for  yield upcaseitem

scala> val list = list("abc", "bcd", "cde")

list: list[string] = list(abc, bcd, cde)
scala>
| val upcaseitems = for  yield upcaseitem
upcaseitems: list[string] = list(abc, bcd, cde)

while (表示式)

var count = 0

do  while(count < 10)

操作&&

和操作||

或操作》

大於》=

大於或等於

<

小於<=

小於或等於

==等於

!=不等於

try  catch  finally

object expensiveresource 

}

// file: enum.scala

object breed extends enumeration 
import breed._
println("id\tbreed")
for (breed <- breed.values) println(s"$\t$breed")
println("\njust terriers:")
breed.values filter (_.tostring.endswith("terrier")) foreach println
def isterrier(b: breed) = b.tostring.endswith("terrier")
println("\njust terriers:")
breed.values filter isterrier foreach println

id      breed

0       doberman pinscher
1       yorkshire terrier
2       scottish terrier
3       great dane
4       portuguese water dog
just terriers:
yorkshire terrier
scottish terrier
just terriers:
yorkshire terrier
scottish terrier

val name = "buck trends"

println(s"hello, $name")

scala> val gross = 100000f

gross: float = 100000.0
scala> val net = 64000f
net: float = 64000.0
scala> val percent = (net / gross) * 100
percent: float = 64.0
scala> println(f"$$$%.2f vs. $$$%.2f or $%.1f%%")
$100000.00 vs. $64000.00 or 64.0%
scala> val s = "%02d: name = %s".format(5, "dean wampler")
s: string = 05: name = dean wampler
// 原生插入器
scala> val name = "dean wampler"
name: string = dean wampler
scala> s"123\n$name\n456"
res1: string =
123dean wampler
456scala> raw"123\n$name\n456"
res2: string = 123\ndean wampler\n456

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