用Scala用星火循环映射方法

Question

嗨，我想在scala中使用"for“到map方法。

我该怎么做呢？

例如，在这里，对于每一行读，我想生成一个随机单词：

val rdd = file.map(line => (line,{
            val chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
            val word = new String;
            val res = new String;
            val rnd = new Random;
            val len = 4 + rnd.nextInt((6-4)+1);

            for(i <- 1 to len){
                val char = chars(rnd.nextInt(51));
                word.concat(char.toString);
            }

            word;
}))

我目前的产出是：

Array[(String, String)] = Array((1,""), (2,""), (3,""), (4,""), (5,""), (6,""), (7,""), (8,""), (9,""), (10,""), (11,""), (12,""), (13,""), (14,""), (15,""), (16,""), (17,""), (18,""), (19,""), (20,""), (21,""), (22,""), (23,""), (24,""), (25,""), (26,""), (27,""), (28,""), (29,""), (30,""), (31,""), (32,""), (33,""), (34,""), (35,""), (36,""), (37,""), (38,""), (39,""), (40,""), (41,""), (42,""), (43,""), (44,""), (45,""), (46,""), (47,""), (48,""), (49,""), (50,""), (51,""), (52,""), (53,""), (54,""), (55,""), (56,""), (57,""), (58,""), (59,""), (60,""), (61,""), (62,""), (63,""), (64,""), (65,""), (66,""), (67,""), (68,""), (69,""), (70,""), (71,""), (72,""), (73,""), (74,""), (75,""), (76,""), (77,""), (78,""), (79,""), (80,""), (81,""), (82,""), (83,""), (84,""), (85,""), (86...

我不知道为什么右边是空的。

Answer 1

word.concat不修改word，而是返回一个新字符串，您可以使word成为一个变量并向其添加新字符串：

var word = new String
....
for {
    ...
    word += char
    ...
}

Answer 2

这里不需要var。是一条内衬

  Seq.fill(len)(chars(rnd.nextInt(51))).mkString

这将通过反复调用len来创建长度为chars(rnd.nextInt(51))的序列，然后将其转化为字符串。

因此，您将得到如下内容：

import org.apache.spark.rdd.RDD
import scala.util.Random

val chars = ('a' to 'z') ++ ('A' to 'Z')

val rdd = file.map(line => {
  val randomWord = {
    val rnd = new Random
    val len = 4 + rnd.nextInt((6 - 4) + 1)
    Seq.fill(len)(chars(rnd.nextInt(chars.length-1))).mkString
  }
  (line, randomWord)
})