Java function for arrays like PHP s join

Question

I want to join a String   with a glue string  Is there a function for this

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This is how I do it   private String join String   input  String delimiter        StringBuilder sb   new StringBuilder        for String value   input                sb append value           sb append delimiter             int length   sb length        if length  gt  0                   Remove the extra delimiter         sb setLength length - delimiter length               return sb toString

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In case you re using Functional Java library and for some reason can t use Streams from Java 8  which might be the case when using Android   Retrolambda plugin   here is a functional solution for you   String joinWithSeparator List lt String gt  items  String separator        return items              bind id - gt  list separator  id                drop 1               foldLeft                       result  item  - gt  result   item                                            Note that it s not the most efficient approach  but it does work good for small lists

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Not in core  no  A search for  java array join string glue  will give you some code snippets on how to achieve this though   e g   public static String join Collection s  String delimiter        StringBuffer buffer   new StringBuffer        Iterator iter   s iterator        while  iter hasNext              buffer append iter next             if  iter hasNext                  buffer append delimiter                       return buffer toString

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In Java 8 you can use   1  Stream API    String   a   new String     a    b    c    String result   Arrays stream a  collect Collectors joining           2  new String join method  https   stackoverflow com a 21756398 466677   3  java util StringJoiner class  http   docs oracle com javase 8 docs api java util StringJoiner html

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Just for the  I ve the shortest one  challenge  here are mines     Iterative   public static String join String s  Object    a        StringBuilder o   new StringBuilder        for  Iterator lt Object gt  i   Arrays asList a  iterator    i hasNext             o append i next    append i hasNext     s            return o toString        Recursive   public static String join String s  Object    a        return a length    0        a 0     a length    1        s   join s  Arrays copyOfRange a  1  a length

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As with many questions lately  Java 8 to the rescue     Java 8 added a new static method to java lang String which does exactly what you want   public static String join CharSequence delimeter  CharSequence    elements     Using it   String s   String join       new String     Hello    World            Results in    Hello  World

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Google guava s library also has this kind of capability  You can see the String   example also from the API   As already described in the api  beware of the immutability of the builder methods   It can accept an array of objects so it ll work in your case  In my previous experience  i tried joining a Stack which is an iterable and it works fine   Sample from me    Deque lt String gt  nameStack   new ArrayDeque lt  gt     nameStack push  a coder    nameStack push  i am    System out println       Joiner on      skipNulls   join nameStack            prints out    i am a coder

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Given   String   a   new String      Hello    World            Then as an alternative to coobird s answer  where the glue is        Arrays asList a  toString   replaceAll                    Or to concatenate with a different string  such as    amp amp      Arrays asList a  toString   replaceAll          amp amp     replaceAll                    However    this one ONLY works if you know that the values in the array or list DO NOT contain the character string

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If you ve landed here looking for a quick array-to-string conversion  try Arrays toString        Creates a String representation of the Object   passed  The result is   surrounded by brackets         each element is converted to a String   via the String valueOf Object  and separated by       If the array is   null  then  null  is returned

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A little mod instead of using substring       join String array delimiter  public static String join String r   String d            if  r length    0  return             StringBuilder sb   new StringBuilder            int i          for i 0 i lt r length-1 i                 sb append r i                sb append d                     sb append r i            return sb toString

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Nothing built-in that I know of   Apache Commons Lang has a class called StringUtils which contains many join functions

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You could easily write such a function in about ten lines of code   String combine String   s  String glue      int k   s length    if   k    0           return null        StringBuilder out   new StringBuilder      out append  s 0       for   int x 1  x  lt  k    x           out append glue  append s x          return out toString

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My spin   public static String join Object   objects  String delimiter      if  objects length    0        return           int capacityGuess    objects length   objects 0  toString   length              objects length - 1    delimiter length       StringBuilder ret   new StringBuilder capacityGuess     ret append objects 0      for  int i   1  i  lt  objects length  i          ret append delimiter       ret append objects i          return ret toString       public static String join Object    objects      return join objects

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I do it this way using a StringBuilder   public static String join String   source  String delimiter        if   null    source      source length  lt  1             return                StringBuilder stringbuilder   new StringBuilder        for  String s   source            stringbuilder append s   delimiter             return stringbuilder toString         join  String    String

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A similar alternative          param delimiter      param inStr     return String     public static String join String delimiter  String    inStr        StringBuilder sb   new StringBuilder        if  inStr length  gt  0                sb append inStr 0            for  int i   1  i  lt  inStr length  i                          sb append delimiter                                  sb append inStr i                        return sb toString

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To get  str1  str2  from  str1    str2         Stream of  str1    str2       filter str - gt   str isEmpty    collect Collectors joining            Also you can add extra null-check

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If you were looking for what to use in android  it is   String android text TextUtils join CharSequence delimiter  Object   tokens    for example   String joined   TextUtils join      MyStringArray

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There is simple shorthand technique I use most of the times     String op   new String  for  int i   is         op    candidatesArr i-1         op   op substring 0  op length  -1

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Starting from Java8 it is possible to use String join     String join       new String    Hello    World           Generates   Hello  World      Otherwise  Apache Commons Lang has a StringUtils class which has a join function which will join arrays together to make a String   For example   StringUtils join new String     Hello    World                 Generates the following String   Hello  World

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java util Arrays has an  asList  method  Together with the java util List ArrayList API this gives you all you need    private static String   join String   array1  String   array2         List lt String gt  list   new ArrayList lt String gt  Arrays asList array1        list addAll Arrays asList array2        return list toArray new String 0

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If you are using the Spring Framework then you have the StringUtils class   import static org springframework util StringUtils arrayToDelimitedString   arrayToDelimitedString new String     A    B    C      n

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Do you like my 3-lines way using only String class s methods   static String join String glue  String   array        String line           for  String s   array  line    s   glue      return  array length    0    line   line substring 0  line length   - glue length

[java] Java function for arrays like PHP's join()?

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