for循環進入使用斯卡拉Spark的地圖方法

您好我想在scala的地圖方法中使用「for」。for循環進入使用斯卡拉Spark的地圖方法

我該怎麼辦呢？

例如這裏的每一行讀我要生成一個隨機單詞：

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; 
}))

我的電流輸出爲：

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...

我不知道爲什麼右側是空的。

來源

2017-01-13 user7375007

word.concat不修改word但返回一個新的字符串，可以使word一個變量，新的字符串添加到它：

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

來源

2017-01-13 03:49:06 Psidom

當我嘗試它，我收到此錯誤錯誤：價值+ =不是字符串字中的一員+ = char.toString – user7375007

需要聲明'word'作爲一個變量。注意'word'前面的'var'關鍵字，而不是'val'，它是不可變的。 – Psidom

是的，你是正確的thx很多！ – user7375007

沒有必要爲var這裏。這是一個內襯

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

這將通過反覆調用chars(rnd.nextInt(51))創建長度len的字符序列，則使得它成爲一個字符串。

因此，你會得到這樣的事情：

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) 
})

來源

2017-01-13 09:27:01

如果你不介意的話，我冒昧地更新了你的答案。 :) – eliasah

如果你喜歡。我認爲這已經很清楚了:)我調整了它 –

for循環進入使用斯卡拉Spark的地圖方法

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