Convert String to comma separated string in java

Question

i have one String     String   name     amit    rahul    surya      i want to send name as parameter in sql query inside IN clause so how do i convert into a format   amit   rahul   surya

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In java 8 for none string array and none primitive object (Long, Integer, ...)

List<Long> ids = Arrays.asList(1l, 2l,3l);
ids.stream().map(String::valueOf).collect(Collectors.joining(","))))

In java 8 for specific field of an objets array (example a car with 2 fields color and speed)

List<Car> cars= Cars.asList(car1, cars2,car3);
    cars.stream().map(Car::getColor).collect(Collectors.joining(","))))

Combine map with valueOf for none String field of an array of objects

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Extention for prior Java 8 solution  String result   String join      name     If you need prefix or  and suffix for array values   StringJoiner joiner   new StringJoiner        for  CharSequence cs  name         joiner add       cs             return joiner toString      Or simple method concept    public static String genInValues String delimiter  String prefix  String suffix  String   name        StringJoiner joiner   new StringJoiner delimiter       for  CharSequence cs  name          joiner add prefix   cs   suffix             return joiner toString          For example   For Oracle i need  id in  1 2 3 4 5    then use genInValues              name     But for Postgres i need  id in  values  1   2   3   4   5    then use genInValues                name

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String   paramIdIdList   P001   P002   P003     StringBuilder builder   new StringBuilder                for String paramId   paramIdIdList                    builder append paramId                                 builder deleteCharAt builder length   -1               String paramIds   builder toString    System Out Println paramIds

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here is a Utility method to split an array and put your custom delimiter  using   String replace String String  Arrays toString Object      here it is    public static String toString String delimiter  Object  array       String s               split array     if  array    null  amp  amp  array length  gt  0            s   Arrays toString array  replace          replace                         place delimiter  notice the space in           if delimiter    null           s   s replace       delimiter              return s      change the second argument type to suite your array type

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Android developers are probably looking for TextUtils join  Android docs   http   developer android com reference android text TextUtils html  Code   String   name     amit    rahul    surya    TextUtils join     name

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You can do this with one line of code   Arrays toString strings  replaceAll             s

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i use this  public static String convertToCommaSeparated String   strings        StringBuffer sb   new StringBuffer          for  int i   0  strings    null  amp  amp  i  lt  strings length  i              sb append strings i            if  i  lt  strings length - 1                sb append                           return sb toString

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USE StringUtils join function  E g    String myCsvString   StringUtils join myList

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String newNameList null    for int i   name length i gt  0 i--       if newNameList  null           newNameList          name name length - i                    else          newNameList            name name length - i

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Either write a simple method yourself  or use one of the various utilities out there   Personally I use apache StringUtils  StringUtils join   edit  in Java 8  you don t need this at all anymore   String joined   String join      name

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If you already have Spring Framework as a dependency  you could also use the very simple util method    org springframework util StringUtils arrayToCommaDelimitedString String   array

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This would be an optimized way of doing it  StringBuilder sb   new StringBuilder    for  String n   arr         sb append      append n  append          if sb length   gt 0      sb setLength sbDiscrep length  -1   return sb toString

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You could also simplify it using the Guava library   String   name     amit    rahul    surya    String str         Joiner on      skipNulls   join name       replace

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You can also use org apache commons lang StringUtils API to form a comma separated result from string array in Java   StringUtils join strArr

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Nice and simple  but java8 required   String result   String join      names

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As tempting and  cool  as the code may appear  do not use fold or reduce on large collections of strings  as these will suffer from the string concatenation problem  String   strings      foo    bar    baz     Optional lt String gt  result   Arrays stream strings           reduce  a  b  - gt  String format   s  s   a  b    System out println result get       Instead  as per other answers  use String join   if you already have a collection  or a StringBuilder if not

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Two lines  excluding declarations   finalstring  should be initially declared equal to an empty string   if you don t care a lot about vertically spacing the for   loop   for  int i   0  i lt string array length  i     finalstring    string array i        finalstring   finalstring substring 0 finalstring length  -1     Two lines  you re done

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String   name     amit    rahul    surya      public static String arrayToString String array          if  array length    0  return         StringBuilder sb   new StringBuilder        for  int i   0  i  lt  array length    i                sb append       append array i   append                 return sb substring 1

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This my be helpful     private static String convertArrayToString String    strArray                StringBuilder builder   new StringBuilder                for int i   0  i lt   strArray length-1  i                      if i    strArray length-1                        builder append     strArray i                         else                       builder append     strArray i                                                        return builder toString

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if  name length  gt  0        StringBuilder nameBuilder   new StringBuilder         for  String n   name            nameBuilder append      append n replace              append                   can also do the following            nameBuilder append      append n replace             append                   nameBuilder deleteCharAt nameBuilder length   - 1        return nameBuilder toString      else       return

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You may also want not to spawn StringBuilder for such simple operation  Please note that I ve changed name of your array from name to names for sake of content conformity   String   names     amit    rahul    surya     String namesString       int delimeters    names size   - 1   for  String name   names      namesString     delimeters--  gt  0          name                name

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use StringBuilder and iterate over your String    and append each String into it   public static String convert String   name         StringBuilder sb   new StringBuilder        for  String st   name             sb append       append st  append       append                 if  name length    0  sb deleteCharAt sb length  -1       return sb toString

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StringBuilder sb   new StringBuilder    for  String n   name         if  sb length    gt  0  sb append           sb append      append n  append         return sb toString

[java] Convert String[] to comma separated string in java

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