learning scala control statement

Posted 2021-02-07 lianghong881018

1 .if satement

 与其它语言不同的是，scala if statement 返回的是一个值

scala> val a = if ( 6 > 0 ) 1 else -1
a: Int = 1

 

2. while statement

3. do.. while statement

4 for statement

　　for ( 变量 <-  表达式 ) ｛ 语句块｝；

scala> for ( i <- 1 to 3 ) println(i)
1
2
3

scala> for ( i <- Array(3,4,5) ) println(i)
3
4
5

scala> for ( i <- 1 to 5 if i%2 == 0 ) println(i)
2
4

scala> for ( i <- 2 to 4; j <- 4 to 6 ) println( i * j)
8
10
12
12
15
18
16
20
24

yield 后的语句块中最后一个表达式的值，作为每次循环的返回值，如下所示：

scala> var fortest = for ( i <- 2 to 4; j <- 4 to 6 ) yield println( i * j)
8
10
12
12
15
18
16
20
24
fortest: scala.collection.immutable.IndexedSeq[Unit] = Vector((), (), (), (), (), (), (), (), ())

scala> var fortest = for ( i <- 2 to 4; j <- 4 to 6 ) yield { println( i * j); i*j }
8
10
12
12
15
18
16
20
24
fortest: scala.collection.immutable.IndexedSeq[Int] = Vector(8, 10, 12, 12, 15, 18, 16, 20, 24)