Scala中的一些内置函数

蔚落 2023-07-09 11:25 18阅读 0赞

## Scala中的一些内置函数 ##

### 1.将字符变为大写【toUpperCase】 ###

val books = List("Hadoop", "Hive", "HDFS")
        println(books.map(_.toUpperCase))

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjgzMDY5Nw_size_16_color_FFFFFF_t_70][]

### 2.将字符变为小写【toLowerCase】 ###

val books = List("Hadoop", "Hive", "HDFS")
    println(books.map(_.toLowerCase))

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjgzMDY5Nw_size_16_color_FFFFFF_t_70 1][]

### 3.将列表元素打平【flatten】 ###

val books = List("Hadoop", "Hive", "HDFS")
    println(books.map(_.toLowerCase))
    println(books.map(_.toLowerCase).flatten)

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjgzMDY5Nw_size_16_color_FFFFFF_t_70 2][]

### 4.将列表元素打平并合并【flatMap】 ###

val books = List("Hadoop", "Hive", "HDFS")
    //    将每一个列表元素都打平
        println(books.flatMap(x=>x))
    //    将每一个列表元素都转为list，然后打平
        println(books.flatMap(_.toList))
    //    将字符串hadoop转化为list，那么每个字母为一个元素
        println("hadoop".toList)
    //    将列表内的每个元素都打平
        println(List("hadoop").flatMap(x=>x))

### 5.取出集合内的每一个元素【foreach】 ###

val l1 = (1 to 10).toList
        l1.foreach(println)

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjgzMDY5Nw_size_16_color_FFFFFF_t_70 3][]

### 6.取出集合内的前n个元素【take】 ###

val l1 = (1 to 10).toList
        println(l1.take(3))

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjgzMDY5Nw_size_16_color_FFFFFF_t_70 4][]

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