How to add elements of a string array to a string array list

Question

I am trying to pass a string array as an argument to the constructor of Wetland class   I don t understand how to add the elements of string array to the string array list   import java util ArrayList   public class Wetland       private String name      private ArrayList lt String gt  species      public Wetland String name  String   speciesArr            this name   name          for  int i   0  i  lt  speciesArr length  i                  species add speciesArr i

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Arrays asList is bridge between Array and collection framework and it returns a fixed size List backed by Array   species   Arrays asList speciesArr

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In Java 8  the syntax for this simplifies greatly and can be used to accomplish this transformation succinctly   Do note  you will need to change your field from a concrete implementation to the List interface for this to work smoothly   public class Wetland       private String name      private List lt String gt  species      public Wetland String name  String   speciesArr            this name   name          species   Arrays stream speciesArr                           collect Collectors toList

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Thought I ll add this one to the mix   Collections addAll result  preprocessor preprocess lines      This is the change that Intelli recommends   from the javadocs    x000D   x000D  Adds all of the specified elements to the specified collection  x000D  Elements to be added may be specified individually or as an array  x000D  The behavior of this convenience method is identical to that of x000D   lt tt gt c addAll Arrays asList elements   lt  tt gt   but this method is likely x000D  to run significantly faster under most implementations  x000D    x000D  When elements are specified individually  this method provides a x000D  convenient way to add a few elements to an existing collection  x000D   lt pre gt  x000D  Collections addAll flavors   Peaches  n Plutonium    Rocky Racoon    x000D   lt  pre gt  x000D   x000D   x000D

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Arrays asList is the handy function available in Java to convert an array variable to List or Collection  For better under standing consider the below example   package com stackoverflow works   import java util ArrayList  import java util Arrays  import java util List   public class Wetland       private String name      private List lt String gt  species   new ArrayList lt String gt          public Wetland String name  String   speciesArr            this name   name          this species   Arrays asList speciesArr              public void display             System out println  Name      name           System out println  Elements in the List            System out println                                  for  String string   species                System out println string                                   Description  Method to test your code             public static void main String   args            String name    Colors           String speciesArr     new String      red    blue    green            Wetland wetland   new Wetland name  speciesArr           wetland display               Output

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ArrayList lt String gt  arraylist  new ArrayList lt String gt      arraylist addAll  Arrays asList  mp3 radio    presvlake    dizalica    sijelice    brisaci farova    neonke    ratkape    kuka    trokut

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public class duplicateArrayList         ArrayList al   new ArrayList        public duplicateArrayList Object   obj             for  int i   0  i  lt  obj length  i                   al add obj i                       Iterator iter   al iterator            while iter hasNext                  System out print     iter next                          public static void main String   args          String   str     A   B   C   D         duplicateArrayList dd   new duplicateArrayList str

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You already have built-in method for that  -  List lt String gt  species   Arrays asList speciesArr     NOTE  - You should use List lt String gt  species not ArrayList lt String gt  species   Arrays asList returns a different ArrayList -  java util Arrays ArrayList which cannot be typecasted to java util ArrayList   Then you would have to use addAll method  which is not so good  So just use List lt String gt   NOTE  - The list returned by Arrays asList is a fixed size list  If you want to add something to the list  you would need to create another list  and use addAll to add elements to it  So  then you would better go with the 2nd way as below  -      String   arr   new String 1       arr 0     rohit       List lt String gt  newList   Arrays asList arr           Will throw  UnsupportedOperationException        newList add  jain       Can t do this       ArrayList lt String gt  updatableList   new ArrayList lt String gt          updatableList addAll newList         updatableList add  jain       OK this is fine        System out println newList            Prints  rohit      System out println updatableList     Prints  rohit  jain

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I prefer this   List lt String gt  temp   Arrays asList speciesArr   species addAll temp     The reason is Arrays asList   method will create a fixed sized List  So if you directly store it into species then you will not be able to add any more element  still its not read-only  You can surely edit your items  So take it into temporary list   Alternative for this is   Collections addAll species  speciesArr     In this case  you can add  edit  remove your items

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Arrays asList   method simply returns List type  char    arr      c   a   t        ArrayList lt Character gt  chars   new ArrayList lt Character gt       To add the array into the list  first convert it to list and then call addAll  List arrList   Arrays asList arr   chars addAll arrList     The following line will cause compiler error  chars addAll Arrays asList arr

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Use asList   method  From java Doc asList  List lt String gt  species   Arrays asList speciesArr

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You should instantiate your ArrayList before trying to add items   private List lt String gt  species   new ArrayList lt String gt

[java] How to add elements of a string array to a string array list?

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