Java collections convert a string to a list of characters

Question

I would like to convert the string containing abc to a list of characters and a hashset of characters  How can I do that in Java     List lt Character gt  charList   new ArrayList lt Character gt   abc  toCharArray

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List lt String gt  result   Arrays asList  abc  split

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The most straightforward way is to use a for loop to add elements to a new List   String abc    abc   List lt Character gt  charList   new ArrayList lt Character gt      for  char c   abc toCharArray        charList add c       Similarly  for a Set   String abc    abc   Set lt Character gt  charSet   new HashSet lt Character gt      for  char c   abc toCharArray        charSet add c

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The lack of a good way to convert between a primitive array and a collection of its corresponding wrapper type is solved by some third party libraries   Guava  a very common one  has a convenience method to do the conversion   List lt Character gt  characterList   Chars asList  abc  toCharArray     Set lt Character gt  characterSet   new HashSet lt Character gt  characterList

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Using Java 8 - Stream Funtion   Converting A String into Character List   ArrayList lt Character gt  characterList    givenStringVariable                                                           chars                                                             mapToObj c- gt   char c                                                            collect collectors toList       Converting A Character List into String    String givenStringVariable    characterList                                              stream                                                map String  valueOf                                               collect Collectors joining

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Use a Java 8 Stream   myString chars   mapToObj i - gt   char  i  collect Collectors toList       Breakdown   myString      chars      Convert to an IntStream      mapToObj i - gt   char  i     Convert int to char  which gets boxed to Character      collect Collectors toList        Collect in a List lt Character gt     I have absolutely no idea why String chars   returns an IntStream

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You can do this without boxing if you use Eclipse Collections   CharAdapter abc   Strings asChars  abc    CharList list   abc toList    CharSet set   abc toSet    CharBag bag   abc toBag      Because CharAdapter is an ImmutableCharList  calling collect on it will return an ImmutableList   ImmutableList lt Character gt  immutableList   abc collect Character  valueOf     If you want to return a boxed List  Set or Bag of Character  the following will work   LazyIterable lt Character gt  lazyIterable   abc asLazy   collect Character  valueOf   List lt Character gt  list   lazyIterable toList    Set lt Character gt  set   lazyIterable toSet    Bag lt Character gt  set   lazyIterable toBag      Note  I am a committer for Eclipse Collections

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IntStream can be used to access each character and add them to the list    String str    abc   List lt Character gt  charList   new ArrayList lt  gt     IntStream range 0 str length    forEach i - gt  charList add str charAt i

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Create an empty list of Character and then make a loop to get every character from the array and put them in the list one by one   List lt Character gt  characterList   new ArrayList lt Character gt     char arrayChar     abc toCharArray    for  char aChar   arrayChar         characterList add aChar       autoboxing

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You will have to either use a loop  or create a collection wrapper like Arrays asList which works on primitive char arrays  or directly on strings    List lt Character gt  list   new ArrayList lt Character gt     Set lt Character gt  unique   new HashSet lt Character gt     for char c    abc  toCharArray          list add c       unique add c       Here is an Arrays asList like wrapper for strings   public List lt Character gt  asList final String string        return new AbstractList lt Character gt             public int size     return string length             public Character get int index    return string charAt index                This one is an immutable list  though  If you want a mutable list  use this with a char     public List lt Character gt  asList final char   string        return new AbstractList lt Character gt             public int size     return string length           public Character get int index    return string index            public Character set int index  Character newVal              char old   string index             string index    newVal            return old                      Analogous to this you can implement this for the other primitive types  Note that using this normally is not recommended  since for every access you would do a boxing and unboxing operation   The Guava library contains similar List wrapper methods for several primitive array classes  like Chars asList  and a wrapper for String in Lists charactersOf String

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In Java8 you can use streams I suppose  List of Character objects   List lt Character gt  chars   str chars        mapToObj e- gt  char e  collect Collectors toList       And set could be obtained in a similar way   Set lt Character gt  charsSet   str chars        mapToObj e- gt  char e  collect Collectors toSet

[java] Java collections convert a string to a list of characters

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