How to convert a List String into a comma separated string without iterating List explicitly

Question

List lt String gt  ids   new ArrayList lt String gt     ids add  1    ids add  2    ids add  3    ids add  4      Now i want an output from this list as 1 2 3 4 without explicitly iterating over it

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On Android use    android text TextUtils join      ids

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Here is code given below to convert a List into a comma separated string without iterating List explicitly for that you have to make a list and add item in it than convert it into a comma separated string  Output of this code will be  Veeru Nikhil Ashish Paritosh   instead of output of list  Veeru Nikhil Ashish Paritosh   String List name  List lt String gt  myNameList   new ArrayList lt String gt     myNameList add  Veeru    myNameList add  Nikhil    myNameList add  Ashish    myNameList add  Paritosh     List name   myNameList toString   replace                               replace          replace

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If you want to convert list into the CSV format             List lt String gt  ids   new ArrayList lt String gt     ids add  1    ids add  2    ids add  3    ids add  4        CSV format String csv   ids toString   replace          replace                       replace                 CSV format surrounded by single quote     Useful for SQL IN QUERY  String csvWithQuote   ids toString   replace           replace                        replace

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One Liner  pure Java   list toString   replace            replaceAll

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I am having ArrayList of String  which I need to convert to comma separated list  without space  The ArrayList toString   method adds square brackets  comma and space  I tried the Regular Expression method as under   List lt String gt  myProductList   new ArrayList lt String gt     myProductList add  sanjay    myProductList add  sameer    myProductList add  anand    Log d  TEST1   myProductList toString              sanjay  sameer  anand   String patternString   myProductList toString   replaceAll     s               Log d  TEST   patternString                       sanjay sameer anand    Please comment for more better efficient logic    The code is for Android   Java    Thankx

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If you re using Eclipse Collections  formerly GS Collections   you can use the makeString   method   List lt String gt  ids   new ArrayList lt String gt     ids add  1    ids add  2    ids add  3    ids add  4     Assert assertEquals  1 2 3 4   ListAdapter adapt ids  makeString          If you can convert your ArrayList to a FastList  you can get rid of the adapter   Assert assertEquals  1 2 3 4   FastList newListWith 1  2  3  4  makeString          Note  I am a committer for Eclipse collections

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import com google common base Joiner   Joiner on      join ids     or you can use StringUtils      public static String join Object   array                                char separator      public static String join Iterable lt   gt  iterator                                char separator    Joins the elements of the provided array iterable into a single String containing the provided list of elements   http   commons apache org proper commons-lang javadocs api-3 3 2 org apache commons lang3 StringUtils html

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The quickest way is   StringUtils join ids

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The following   String joinedString   ids toString     will give you a comma delimited list  See docs for details   You will need to do some post-processing to remove the square brackets  but nothing too tricky

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Join   concat  amp  Split functions on ArrayList   To Join  concat all elements of arraylist with comma       to String   List lt String gt  ids   new ArrayList lt String gt     ids add  1    ids add  2    ids add  3    ids add  4    String allIds   TextUtils join      ids   Log i  Result   allIds     To split all elements of String to arraylist  with comma         String allIds    1 2 3 4   String   allIdsArray   TextUtils split allIds        ArrayList lt String gt  idsList   new ArrayList lt String gt  Arrays asList allIdsArray    for String element   idsList       Log i  Result   element       Done

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Java 8 solution if it s not a collection of strings    Any collection  stream        collect StringBuilder  new  StringBuilder  append  StringBuilder  append       toString

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With Java 8   String csv   String join      ids     With Java 7-  there is a dirty way  note  it works only if you don t insert strings which contain      in your list  - obviously  List toString will perform a loop to create idList but it does not appear in your code   List lt String gt  ids   new ArrayList lt String gt     ids add  1    ids add  2    ids add  3    ids add  4    String idList   ids toString    String csv   idList substring 1  idList length   - 1  replace

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You can use below code if object has attibutes under it   String getCommonSeperatedString List lt ActionObject gt  actionObjects        StringBuffer sb   new StringBuffer        for  ActionObject actionObject   actionObjects           sb append actionObject Id  append                 sb deleteCharAt sb lastIndexOf            return sb toString

[java] How to convert a List<String> into a comma separated string without iterating List explicitly

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