how to convert a String sentence to arraylist in Kotlin

Question

I have this function to convert string sentence to list words. I created this function in Java and converted to Kotlin using default Kotlin conversion in Android Studio, but I believe there can be many ways to shorten this code in Awesome Kotlin. I will be good if you can share your piece of code and help me(and all) to improve our knowledge in Kotlin.

private fun stringToWords(mnemonic: String): List<String> {
    val words = ArrayList<String>()
    for (word in mnemonic.trim { it <= ' ' }.split(" ".toRegex()).dropLastWhile { it.isEmpty() }.toTypedArray()) {
        if (word.isNotEmpty()) {
            words.add(word)
        }
    }
    return words
}

Can you share the original java function as well?

Abdul-Aziz-Niazi
– Abdul-Aziz-Niazi

2018-11-28 05:23:10 +00:00
Commented Nov 28, 2018 at 5:23 — Abdul-Aziz-Niazi
– Abdul-Aziz-Niazi, Commented Nov 28, 2018 at 5:23
gist.github.com/januprasad/8e4f2a8f520e0f8839bbe8e23496ac04

J.K
– J.K

2018-11-28 05:27:03 +00:00
Commented Nov 28, 2018 at 5:27 — J.K
– J.K, Commented Nov 28, 2018 at 5:27

Roland · Accepted Answer · 2018-11-28 06:30:37Z

21

I would go for the following:

fun stringToWords(s : String) = s.trim().splitToSequence(' ')
    .filter { it.isNotEmpty() } // or: .filter { it.isNotBlank() }
    .toList()

Note that you probably want to adjust that filter, e.g. to filter out blank entries too... I put that variant in the comment... (if you use that one, you do not require an initial trim() though)

If you rather want to work with the Sequence you can do so by just omitting the .toList() at the end.

And as also Abdul-Aziz-Niazi said: same is also possible via extension function, if you require it more often:

fun String.toWords() = trim().splitToSequence(' ').filter { it.isNotEmpty() }.toList()

edited Nov 28, 2018 at 6:30

answered Nov 28, 2018 at 6:09

Roland

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1 Comment

J.K Over a year ago

I Liked it very much because you're doing in Kotlin Way.

Shivesh Karan Mehta · Accepted Answer · 2018-11-28 06:16:23Z

3

You can do it like this.. Just make a function of return type list.

 val s = "This is a sample sentence."

 val words:Array<String>  = s.split("\\s+".toRegex()).dropLastWhile { it.isEmpty() }.toTypedArray()
    for (i in words.indices) {
        // You may want to check for a non-word character before blindly
        // performing a replacement
        // It may also be necessary to adjust the character class
        words[i] = words[i].replace("[^\\w]".toRegex(), "")
    }

May this will help you :-)

answered Nov 28, 2018 at 6:16

Shivesh Karan Mehta

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Comments

forpas · Accepted Answer · 2018-11-28 06:35:58Z

3

It's easier than you think:

fun stringToWords(mnemonic: String) = mnemonic.replace("\\s+".toRegex(), " ").trim().split(" ")

Remove multiple spaces, trim start and the end, split.
Like an extention:

fun String.toWords() = replace("\\s+".toRegex(), " ").trim().split(" ")

After Roland's suggestion:

fun String.toWords() = trim().split("\\s+".toRegex())

edited Nov 28, 2018 at 6:35

answered Nov 28, 2018 at 6:06

forpas

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Comments

J.K · Accepted Answer · 2018-11-28 06:14:42Z

1

You don't need scopes, the redundant "".toRegex() and the last expression. You can do something like this:

private fun stringToWords(mnemonic: String): List<String> {
    val words = ArrayList<String>()
    for (w in mnemonic.trim(' ').split(" ")) {
        if (w.isNotEmpty()) {
            words.add(w)
        }
    }
    return words
}

Additionally, If you use this method a lot in this project, you can make it an extension in string class. Paste this method in a separate file(outside a classes or add it in classless .kt file) so it has a global access. and then you can use it with any string like myString.toWords() anywhere in the project The method will look like this

inline fun String.toWords(): List<String> {
    val words = ArrayList<String>()
    for (w in this.trim(' ').split(" ")) {
        if (w.isNotEmpty()) {
            words.add(w)
        }
    }
    return words
}

edited Nov 28, 2018 at 6:14

J.K

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answered Nov 28, 2018 at 5:38

Abdul-Aziz-Niazi

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1 Comment

J.K Over a year ago

Yeah, I heard of Extensions. Great Good Answer.

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