How to convert a String into an ArrayList

Question

In my String  I can have an arbitrary number of words which are comma separated  I wanted each word added into an ArrayList  E g    String s    a b c d e

User · Answer

I recommend use the StringTokenizer  is very efficient        List lt String gt  list   new ArrayList lt  gt           StringTokenizer token   new StringTokenizer value  LIST SEPARATOR        while  token hasMoreTokens                 list add token nextToken

User · Answer

Try something like  List lt String gt  myList   new ArrayList lt String gt  Arrays asList s split            Arrays asList documentation String split documentation ArrayList Collection  constructor documentation     Demo   String s    lorem ipsum dolor sit amet    List lt String gt  myList   new ArrayList lt String gt  Arrays asList s split          System out println myList       prints  lorem  ipsum  dolor  sit  amet      This post has been rewritten as an article here

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Let s take a question   Reverse a String  I shall do this using stream   collect    But first I shall change the string into an ArrayList        public class StringReverse1       public static void main String   args             String a    Gini Gina  Proti            List lt String gt  list   new ArrayList lt String gt  Arrays asList a split                 list stream            collect Collectors toCollection  LinkedList    new             descendingIterator            forEachRemaining System out  println                The output   i t o r P   a n i G  i n i G

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If you re using guava  and you should be  see effective java item  15    ImmutableList lt String gt  list   ImmutableList copyOf s split

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This is using Gson in Kotlin      val listString     uno dos tres cuatro cinco    val gson   Gson    val lista   gson fromJson listString   Array lt String gt   class java  toList    Log e  GSON   lista 0

User · Answer

Easier to understand is like this   String s    a b c d e   String   sArr   s split       List lt String gt  sList   Arrays asList sArr

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Ok i m going to extend on the answers here since a lot of the people who come here want to split the string by a whitespace  This is how it s done   List lt String gt  List   new ArrayList lt String gt  Arrays asList s split    s

User · Answer

If you want to convert a string into a ArrayList try this   public ArrayList lt Character gt  convertStringToArraylist String str        ArrayList lt Character gt  charList   new ArrayList lt Character gt               for int i   0  i lt str length   i             charList add str charAt i              return charList      But i see a string array in your example  so if you wanted to convert a string array into ArrayList use this   public static ArrayList lt String gt  convertStringArrayToArraylist String   strArr       ArrayList lt String gt  stringList   new ArrayList lt String gt         for  String s   strArr            stringList add s             return stringList

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In Java 9  using List of  which is an Immutable List Static Factory Methods  become more simpler    String s    a b c d e              List lt String gt  lst   List of s split

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If you are importing or you have an array  of type string  in your code and you have to convert it into arraylist  offcourse string  then use of collections is better  like this   String array1     getIntent   getExtras   getStringArray  key1    or String array1         then  List allEds   new ArrayList    Collections addAll allEds  array1

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You could use             List lt String gt  tokens   Arrays stream s split    s     collect Collectors toList       You should ask yourself if you really need the ArrayList in the first place  Very often  you re going to filter the list based on additional criteria  for which a Stream is perfect  You may want a set  you may want to filter them by means of another regular expression  etc  Java 8 provides this very useful extension  by the way  which will  work on any CharSequence  https   docs oracle com javase 8 docs api java util regex Pattern html splitAsStream-java lang CharSequence-  Since you don t need the array at all  avoid creating it thus       This will presumably be a static final field somewhere  Pattern splitter   Pattern compile    s            String untokenized   reader readLine    Stream lt String gt  tokens   splitter splitAsStream untokenized

User · Answer

Option1    List lt String gt  list   Arrays asList  hello      Option2   List lt String gt  list   new ArrayList lt String gt  Arrays asList  hello       In my opinion  Option1 is better because    we can reduce the number of ArrayList objects being created from 2 to 1  asList method creates and returns an ArrayList Object  its performance is much better  but it returns a fixed-size list     Please refer to the documentation here

User · Answer

String s1   a b c d     String replace   s1 replace           System out println replace    String replace1   replace replace           System out println replace1    List lt String gt  myList   new ArrayList lt String gt  Arrays asList replace1 split          System out println myList toString

[java] How to convert a String into an ArrayList?

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