Converting ArrayList String to String in Java

Question

How might I convert an ArrayList lt String gt  object to a String   array in Java

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List  lt String gt  list       String   array   new String list size     int i 0  for String s  list     array i      s

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An alternative in Java 8   String   strings   list stream   toArray String    new     Java 11    String   strings   list toArray String    new

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Starting from Java-11  one can alternatively use the API Collection toArray IntFunction lt T   gt  generator  to achieve the same as   List lt String gt  list   List of  x   y   z    String   arrayBeforeJDK11   list toArray new String 0    String   arrayAfterJDK11   list toArray String    new      similar to Stream toArray

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Generics solution to covert any List lt Type gt  to String      public static   lt T gt  String   listToArray List lt T gt  list        String    array   new String list size         for  int i   0  i  lt  array length  i            array i    list get i  toString        return array      Note You must override toString   method   class Car     private String name    public Car String name        this name   name        public String toString         return name        final List lt Car gt  carList   new ArrayList lt Car gt     carList add new Car  BMW    carList add new Car  Mercedes    carList add new Car  Skoda    final String   carArray   listToArray carList

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You can use Iterator lt String gt  to iterate the elements of the ArrayList lt String gt    ArrayList lt String gt  list   new ArrayList lt  gt     String   array   new String list size     int i   0  for  Iterator lt String gt  iterator   list iterator    iterator hasNext    i          array i    iterator next        Now you can retrive elements from String   using any Loop

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in case some extra manipulation of the data is desired  for which the user wants a function  this approach is not perfect  as it requires passing the class of the element as second parameter   but works   import java util ArrayList  import java lang reflect Array   public class Test     public static void main String   args        ArrayList lt Integer gt  al   new ArrayList lt  gt         al add 1       al add 2       Integer   arr   convert al  Integer class       for  int i 0  i lt arr length  i          System out println arr i           public static  lt T gt  T   convert ArrayList lt T gt  al  Class clazz        return  T    al toArray  T   Array newInstance clazz  al size

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In Java 11  we can use the Collection toArray generator  method  The following code will create a new array of strings   List lt String gt  list   List of  one    two    three    String   array   list toArray String    new    from java base s  java util Collection toArray

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If your application is already using Apache Commons lib  you can slightly modify the accepted answer to not create a new empty array each time   List lt String gt  list       String   array   list toArray ArrayUtils EMPTY STRING ARRAY       or if using static import String   array   list toArray EMPTY STRING ARRAY     There are a few more preallocated empty arrays of different types in ArrayUtils   Also we can trick JVM to create en empty array for us this way   String   array   list toArray ArrayUtils toArray         or if using static import String   array   list toArray toArray       But there s really no advantage this way  just a matter of taste  IMO

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In Java 8   String   strings   list parallelStream   toArray String    new

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You can use the toArray   method for List   ArrayList lt String gt  list   new ArrayList lt String gt      list add  apple    list add  banana     String   array   list toArray new String list size        Or you can manually add the elements to an array   ArrayList lt String gt  list   new ArrayList lt String gt      list add  apple    list add  banana     String   array   new String list size      for  int i   0  i  lt  list size    i          array i    list get i       Hope this helps

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private String   prepareDeliveryArray List lt DeliveryServiceModel gt  deliveryServices        String   delivery   new String deliveryServices size         for  int i   0  i  lt  deliveryServices size    i              delivery i    deliveryServices get i  getName              return delivery

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ArrayList lt String gt  arrayList   new ArrayList lt String gt     Object   objectList   arrayList toArray    String   stringArray    Arrays copyOf objectList objectList length String   class     Using copyOf  ArrayList to arrays might be done also

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List lt String gt  list   new ArrayList lt  gt         list add  a        list add  b        list add  c        String    strArry  list stream   toArray size - gt  new String size      Per comments  I have added a paragraph to explain how the conversion works   First  List is converted to a String stream  Then it uses Stream toArray to convert the elements in the stream to an Array  In the last statement above  size -  new String size   is actually an IntFunction function that allocates a String array with the size of the String stream  The statement is identical to  IntFunction lt String    gt  allocateFunc   size - gt     return new String size         String    strArry  list stream   toArray allocateFunc

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In Java 8  it can be done using  String   arrayFromList   fromlist stream   toArray String    new

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List lt String gt  list       String   array   list toArray new String 0      For example   List lt String gt  list   new ArrayList lt String gt       add some stuff list add  android    list add  apple    String   stringArray   list toArray new String 0      The toArray   method without passing any argument returns Object    So you have to pass an array as an argument  which will be filled with the data from the list  and returned  You can pass an empty array as well  but you can also pass an array with the desired size   Important update  Originally the code above used new String list size     However  this blogpost reveals that due to JVM optimizations  using new String 0  is better now

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You can convert List to String array by using this method    Object   stringlist list toArray      The complete example   ArrayList lt String gt  list new ArrayList lt  gt         list add  Abc        list add  xyz         Object   stringlist list toArray         for int i   0  i  lt  stringlist length   i                    Log wtf  list data    String stringlist i

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We have following three ways for converting arraylist to array  public  T   toArray T   a  - In this way we will create a array with size of list then put in method as String   arr   new String list size     arr   list toArray arr    Public get   method - In this way we iterate list and put element in array one by one   Reference   How to convert ArrayList To Array In Java

[java] Converting 'ArrayList<String> to 'String[]' in Java

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