How to find nth occurrence of character in a string

Question

Similar to a question posted here  am looking for a solution in Java   That is  how to find the index of nth occurrence of a character string from a string   Example    folder1 folder2 folder3     In this case  if I ask for 3rd occurrence of slash      it appears before folder3  and I expect to return this index position   My actual intention is to substring it from nth occurrence of a character   Is there any convenient ready-to-use method available in Java API or do we need to write a small logic on our own to solve this   Also     I quickly searched whether any method is supported for this purpose at Apache Commons Lang s StringUtils  but I don t find any  Can regular expressions help in this regard

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Another approach   public static void main String   args        String str     folder1 folder2 folder3         int index   nthOccurrence str       3       System out println index      public static int nthOccurrence String s  char c  int occurrence        return nthOccurrence s  0  c  0  occurrence      public static int nthOccurrence String s  int from  char c  int curr  int expected        final int index   s indexOf c  from       if index    -1  return -1      return  curr   1    expected    index            nthOccurrence s  index   1  c  curr   1  expected

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May be you could achieve this through String split     method also   String str       String   tokens   str split      return tokens nthIndex     null

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2            Match anything followed by   two times  then again  The third one is the one you want  The Matcher state can be used to tell where the last   is

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If your project already depends on Apache Commons you can use StringUtils ordinalIndexOf  otherwise  here s an implementation   public static int ordinalIndexOf String str  String substr  int n        int pos   str indexOf substr       while  --n  gt  0  amp  amp  pos    -1          pos   str indexOf substr  pos   1       return pos        This post has been rewritten as an article here

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program to find nth occurence of a character     import java util Scanner   public class CharOccur1        public static void main String arg                  Scanner scr new Scanner System in           int position -1 count 0          System out println  enter the string            String str scr nextLine            System out println  enter the nth occurence of the character            int n Integer parseInt scr next             int leng str length            char c   new char leng           System out println  Enter the character to find            char key scr next   charAt 0           c str toCharArray            for int i 0 i lt c length i                          if c i   key                                count                    position i                  if count  n                                        System out println  Character found                        System out println  the position at which the     count     ocurrence occurs is     position                       return                                                    if n gt count                         System out println  Character occurs     count     times                return

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public static int nth String source  String pattern  int n        int i   0  pos   0  tpos   0      while  i  lt  n           pos   source indexOf pattern         if  pos  gt  -1             source   source substring pos 1            tpos    pos 1           i            else            return -1                   return tpos - 1

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Two simple options occur    Use charAt   repeatedly Use indexOf   repeatedly   For example   public static int nthIndexOf String text  char needle  int n        for  int i   0  i  lt  text length    i                  if  text charAt i     needle                        n--              if  n    0                                return i                                    return -1      That may well not perform as well as using indexOf repeatedly  but it s possibly simpler to get right

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scala    throw s -1 if the value isn t present for nth time  even if it is present till n-1 th time     throw s index if the value is present for nth time def indexOfWithNumber tempString String valueString String numberOfOccurance Int  Int   var stabilizeIndex 0  var tempSubString tempString  var tempIndex tempString indexOf valueString   breakable   for   i  lt - 1 to numberOfOccurance  if   tempSubString indexOf valueString     -1   amp  amp   tempIndex    -1     tempIndex tempSubString indexOf valueString  tempSubString tempSubString substring tempIndex 1 tempSubString size     ADJUSTING FOR 0 stabilizeIndex stabilizeIndex tempIndex 1    ADJUSTING FOR 0   else    stabilizeIndex  -1 tempIndex  0 break     stabilizeIndex match   case value if value  lt   -1   gt  -1 case     gt  stabilizeIndex-1      reverting for adjusting 0 previously     indexOfWithNumber  quot bbcfgtbgft quot   quot b quot  3     6 indexOfWithNumber  quot bbcfgtbgft quot   quot b quot  2    1 indexOfWithNumber  quot bbcfgtbgft quot   quot b quot  4    -1  indexOfWithNumber  quot bbcfgtbcgft quot   quot bc quot  1     1 indexOfWithNumber  quot bbcfgtbcgft quot   quot bc quot  4    -1 indexOfWithNumber  quot bbcfgtbcgft quot   quot bc quot  2    6

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Nowadays there IS support of Apache Commons Lang s StringUtils   This is the primitive   int org apache commons lang StringUtils ordinalIndexOf CharSequence str  CharSequence searchStr  int ordinal    for your problem you can code the following  StringUtils ordinalIndexOf uri       3   You can also find the last nth occurrence of a character in a string with the lastOrdinalIndexOf method

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public static int findNthOccurrence String phrase  String str  int n        int val   0  loc   -1      for int i   0  i  lt   phrase length  -str length    amp  amp  val  lt  n  i                  if str equals phrase substring i i str length                            val                loc   i                       if val    n          return loc      else         return -1

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The code returns the nth occurrence positions substring aka field width  Example  if  string  Stack overflow in low melow  is the string to search 2nd occurance of  token  low   you will agree with me that it 2nd occurance is at subtring  18 and 21   indexOfOccurance  Stack overflow in low melow   low  2  returns 18 and 21 in a string   class Example      public Example                      public String indexOfOccurance String string  String token  int nthOccurance                        int lengthOfToken   token length                        int nthCount   0                      for  int shift   0 count   0  count  lt  string length   - token length     2  count    shift    lengthOfToken                            if  string substring shift  lengthOfToken  equalsIgnoreCase token                             keeps count of nthOccurance                             nthCount                             if  nthCount    nthOccurance                         checks if nthCount     nthOccurance  If true  then breaks                               return String valueOf shift        String valueOf lengthOfToken                                                                            return  -1                         public static void main String args         Example example   new Example        String string    the man  the woman and the child       int nthPositionOfThe   3     System out println  3rd Occurance of the is at     example indexOfOccurance string   the   nthPositionOfThe

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My solution          Like String indexOf  but find the n th occurance of c     param s string to search     param c character to search for     param n n th character to seach for  starting with 1     return the position  0-based  of the found char  or -1 if failed      public static int nthIndexOf String s  char c  int n        int i   -1      while  n--  gt  0            i   s indexOf c  i   1           if  i    -1              break            return i

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You can try something like this   import java util regex Matcher  import java util regex Pattern   public class Main       public static void main String   args          System out println from3rd   folder1 folder2 folder3                 private static Pattern p   Pattern compile           2                  public static String from3rd String in            Matcher m   p matcher in            if  m matches                return m group 2           else             return null            Note that I did some assumptions in the regex    the input path is absolute  i e  starts with       you do not need the 3rd     in the result      As requested in a comment  I ll try to explain the regex           2                     is a   followed by        any number of characters that are not a              groups the previous expression in a single entity  This is the 1st group of the expression           2  means that the group must match extactly  2  times        is again any number of characters that are not a            groups the previos expression in a single entity  This is the 2nd group of the expression    This way you have only to get the substring that matches the 2nd group  return m group 2    Image courtesy by Debuggex

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This answer improves on  aioobe  s answer  Two bugs in that answer were fixed  1  n 0 should return -1  2  nth occurence returned -1  but it worked on n-1th occurences   Try this        public int nthOccurrence String str  char c  int n        if n  lt   0           return -1            int pos   str indexOf c  0       while  n--  gt  1  amp  amp  pos    -1          pos   str indexOf c  pos 1       return pos

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I made a few changes to aioobe s answer and got a nth lastIndexOf version  and fix some NPE  problems  See code below   public int nthLastIndexOf String str  char c  int n            if  str    null    n  lt  1              return -1          int pos   str length            while  n--  gt  0  amp  amp  pos    -1              pos   str lastIndexOf c  pos - 1           return pos

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I believe the easiest solution for finding the Nth occurrence of a String is to use StringUtils ordinalIndexOf   from Apache Commons   Example   StringUtils ordinalIndexOf  aabaabaa    b   2      5

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public class Sam Stringnth        public static void main String   args            String str  abcabcabc           int n   nthsearch str   c   3           if n lt  0              System out println  Character not found            else             System out println  Position is   n             public static int nthsearch String str  char ch  int n           int pos 0          if n  0               for int i 1  i lt  n i                     pos   str indexOf ch  pos  1                            return pos                    else              return 0

[java] How to find nth occurrence of character in a string?

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