Indexes of all occurrences of character in a string

Question

The following code will print 2  String word    bannanas   String guess    n   int index  System out println       index   word indexOf guess       I would like to know how to get all the indexes of  n    guess   in the string  bannanas   The expected result would be   2 3 5

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This can be done by iterating myString and shifting fromIndex parameter in indexOf       int currentIndex   0     while       myString indexOf        mySubstring        currentIndex   gt   0         System out println currentIndex        currentIndex

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This should print the list of positions without the -1 at the end that Peter Lawrey s solution has had   int index   word indexOf guess   while  index  gt   0        System out println index       index   word indexOf guess  index   1       It can also be done as a for loop   for  int index   word indexOf guess        index  gt   0       index   word indexOf guess  index   1         System out println index        Note  if guess can be longer than a single character  then it is possible  by analyzing the guess string  to loop through word faster than the above loops do  The benchmark for such an approach is the Boyer-Moore algorithm  However  the conditions that would favor using such an approach do not seem to be present

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With Java9  one can make use of the iterate int seed  IntPredicate hasNext IntUnaryOperator next  as follows -  List lt Integer gt  indexes   IntStream            iterate word indexOf c   index - gt  index  gt   0  index - gt  word indexOf c  index   1              boxed              collect Collectors toList     System out printlnt indexes

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int index   -1  while  index   text indexOf  on   index   1    gt   0       LOG d  index     index

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Also  if u want to find all indexes of a String in a String   int index   word indexOf guess   while  index  gt   0        System out println index       index   word indexOf guess  index   guess length

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String string    bannanas   ArrayList lt Integer gt  list   new ArrayList lt Integer gt     char character    n   for int i   0  i  lt  string length    i         if string charAt i     character          list add i             Result would be used like this        for Integer i   list           System out println i           Or as a array    list toArray

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This is a java 8 solution  public int   solution  String s  String subString           int initialIndex   s indexOf subString           List lt Integer gt  indexList   new ArrayList lt  gt             while  initialIndex  gt  0               indexList add initialIndex               initialIndex   s indexOf subString  initialIndex 1                     int    intA   indexList stream   mapToInt i- gt i  toArray            return intA

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Try the following  Which does not print -1 at the end now    int index   word indexOf guess   while index  gt   0       System out println index      index   word indexOf guess  index 1

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Try this  String str    helloslkhellodjladfjhello   String findStr    hello    System out println StringUtils countMatches str  findStr

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This can be done in a functional way with Java 9 using regular expression  Pattern compile Pattern quote guess      sanitize input and create pattern              matcher word     create matcher              results          get the MatchResults  Java 9 method              map MatchResult  start     get the first index              collect Collectors toList       collect found indices into a list         Here s the Kotlin Solution to add this logic as a new a new methods into CharSequence API using extension method      Extension method fun CharSequence indicesOf input  String   List lt Int gt        Regex Pattern quote input      build regex          findAll this              get the matches          map   it range first      get the index          toCollection mutableListOf       collect the result as list     call the methods as  quot Banana quot  indicesOf  quot a quot       1  3  5

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String word    bannanas    String guess    n    String temp   word   while temp indexOf guess     -1         int index   temp indexOf guess        System out println index        temp   temp substring index   1

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I had this problem as well  until I came up with this method   public static int   indexesOf String s  String flag        int flagLen   flag length        String current   s      int   res   new int s length         int count   0      int base   0      while current contains flag             int index   current indexOf flag           res count    index   base          base    index   flagLen          current   current substring current indexOf flag    flagLen  current length                count            return Arrays copyOf res  count       This method can be used to find indexes of any flag of any length in a string  for example   public class Main        public static void main String   args            int   indexes   indexesOf  Hello  yellow jello    ll                Prints  2  9  16          System out println Arrays toString indexes               public static int   indexesOf String s  String flag            int flagLen   flag length            String current   s          int   res   new int s length             int count   0          int base   0          while current contains flag                 int index   current indexOf flag               res count    index   base              base    index   flagLen              current   current substring current indexOf flag    flagLen  current length                    count                    return Arrays copyOf res  count

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A class for splitting strings I came up with  A short test is provided at the end   SplitStringUtils smartSplitToShorterStrings String str  int maxLen  int maxParts  will split by spaces without breaking words  if possible  and if not  will split by indexes according to maxLen    Other methods provided to control how it is split  bruteSplitLimit String str  int maxLen  int maxParts   spaceSplit String str  int maxLen  int maxParts    public class SplitStringUtils      public static String   smartSplitToShorterStrings String str  int maxLen  int maxParts        if  str length    lt   maxLen          return new String    str             if  str length    gt  maxLen maxParts          return bruteSplitLimit str  maxLen  maxParts              String   res   spaceSplit str  maxLen  maxParts       if  res    null          return res             return bruteSplitLimit str  maxLen  maxParts          public static String   bruteSplitLimit String str  int maxLen  int maxParts        String   bruteArr   bruteSplit str  maxLen       String   ret   Arrays stream bruteArr             limit maxParts             collect Collectors toList               toArray new String maxParts        return ret         public static String   bruteSplit String name  int maxLen        List lt String gt  res   new ArrayList lt  gt         int start  0      int end   maxLen      while  end  lt   name length            String substr   name substring start  end         res add substr         start   end        end   maxLen            String substr   name substring start  name length         res add substr       return res toArray new String res size             public static String   spaceSplit String str  int maxLen  int maxParts        List lt Integer gt  spaceIndexes   findSplitPoints str            List lt Integer gt  goodSplitIndexes   new ArrayList lt  gt         int goodIndex   -1       int curPartMax   maxLen      for  int i 0  i lt  spaceIndexes size    i            int idx   spaceIndexes get i         if  idx  lt  curPartMax            goodIndex   idx          else           goodSplitIndexes add goodIndex 1           curPartMax   goodIndex 1 maxLen                    if  goodSplitIndexes get goodSplitIndexes size  -1     str length            goodSplitIndexes add str length               if  goodSplitIndexes size   lt  maxParts          List lt String gt  res   new ArrayList lt  gt           int start   0        for  int i 0  i lt goodSplitIndexes size    i              int end   goodSplitIndexes get i           if  end-start  gt  maxLen              return null                    res add str substring start  end            start   end                return res toArray new String res size                return null          private static List lt Integer gt  findSplitPoints String str  char c        List lt Integer gt  list   new ArrayList lt Integer gt         for  int i   0  i  lt  str length    i            if  str charAt i     c            list add i                     list add str length         return list          Simple test code     public static void main String   args        String    testStrings              123            123 123 123 1123 123 123 123 123 123 123            123 54123 5123 513 54w567 3567 e56 73w45 63 567356 735687 4678 4678 u4678 u4678 56rt64w5 6546345            1345678934576235784620957029356723578946            12764444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444            3463356 35673567567 3567 35 3567 35 675 653 673567 777777777777777777777777777777777777777777777777777777777777777777              int max   35      int maxparts   2        for  String str   testStrings          System out println  TEST n       str             printSplitDetails max  maxparts         String   res   smartSplitToShorterStrings str  max  maxparts         for  int i 0  i lt  res length i              System out println      i      res i                  System out println                                                                                                                                                                               static void printSplitDetails int max  int maxparts        System out print    X          for  int i 0  i lt max maxparts  i            if  i max    0            System out print               else           System out print  -                      System out println

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String input    GATATATGCG       String substring    G       String temp   input      String indexOF          int tempIntex 1       while temp indexOf substring     -1                int index   temp indexOf substring           indexOF    index tempIntex               tempIntex   index 1           temp   temp substring index   1             Log e  indexOf        indexOF

[java] Indexes of all occurrences of character in a string

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