Find duplicate characters in a String and count the number of occurances using Java

Question

How can I find the number of occurrences of a character in a string   For example  The quick brown fox jumped over the lazy dog   Some example outputs are below     a    1  o    4  space    8       1

User · Answer

You can also achieve it by iterating over your String and using a switch to check each individual character, adding a counter whenever it finds a match. Ah, maybe some code will make it clearer:

Main Application:

public static void main(String[] args) {

        String test = "The quick brown fox jumped over the lazy dog.";

        int countA = 0, countO = 0, countSpace = 0, countDot = 0;

        for (int i = 0; i < test.length(); i++) {
            switch (test.charAt(i)) {
                case 'a':
                case 'A': countA++; break;
                case 'o':
                case 'O': countO++; break;
                case ' ': countSpace++; break;
                case '.': countDot++; break;
            }
        }

        System.out.printf("%s%d%n%s%d%n%s%d%n%s%d", "A: ", countA, "O: ", countO, "Space: ", countSpace, "Dot: ", countDot);

    }

Output:

A: 1
O: 4
Space: 8
Dot: 1

User · Answer

Java 8 way    The quick brown fox jumped over the lazy dog            chars            mapToObj i - gt   char  i           collect Collectors groupingBy Object  toString  Collectors counting

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public class StringCountwithOutHashMap     public static void main String   args        System out println  Plz Enter Your String          Scanner sc   new Scanner System in       String s1   sc nextLine        int count   0      for  int i   0  i  lt  s1 length    i              for  int j   0  j  lt  s1 length    j                  if  s1 charAt i     s1 charAt j                     count                                      System out println s1 charAt i      -- gt      count           String d   String valueOf s1 charAt i   trim            s1   s1 replaceAll d               count   0

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Use google guava Multiset lt String gt     Multiset lt String gt  wordsMultiset   HashMultiset create    wordsMultiset addAll words   for Multiset Entry lt E gt  entry wordsMultiset entrySet          System out println entry getElement     -   entry getCount

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import java util HashMap  import java util Map  import java util Scanner  import java util Set  public class DuplicateCountChar       public static void main String   args            Scanner inputString   new Scanner System in           String token   inputString nextLine            char   ch   token toCharArray            Map lt Character  Integer gt  dupCountMap    new HashMap lt Character Integer gt              for  char c   ch                if dupCountMap containsKey c                      dupCountMap put c  dupCountMap get c  1                else                   dupCountMap put c  1                                     for  char c   ch                System out println  Key     c   Value     dupCountMap get c                       Set lt Character gt  keys   dupCountMap keySet            for  Character character   keys                System out println  Key     character    Value       dupCountMap get character

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import java util HashMap  import java util Scanner    public class HashMapDemo        public static void main String   args              Create HashMap object to Store Element as Key and Value          HashMap lt Character Integer gt  hm  new HashMap lt Character Integer gt               Enter Your String From Console         System out println  Enter an String               Create Scanner Class Object From Retrive the element from console to our java application         Scanner sc   new Scanner System in             Store Data in an string format         String s1 sc nextLine              find the length of an string and check that hashmap object contain the character or not by using            containskey   if that map object contain element only one than count that value as one or if it contain more than one than increment value           for int i 0 i lt s1 length   i                 if  hm containsKey s1 charAt i                     hm put s1 charAt i   Integer 1                  if             else                  hm put s1 charAt i  hm get s1 charAt i   1                  else             for          System out println  The Charecters are   hm          main    HashMapDemo

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Finding the duplicates in a String   Example 1   Using HashMap  public class a36       public static void main String   args            String a    Gini Rani           fix a          main     public static void fix String a            Map lt Character  Integer gt  map   new HashMap lt  gt             for  int i   0  i  lt a length     i               char ch   a charAt i                   map put ch   map getOrDefault ch 0   1               for         List lt Character gt  list   new ArrayList lt  gt            Set lt Map Entry lt Character  Integer gt   gt  entrySet   map entrySet            for    Map Entry lt Character  Integer gt  entry   entrySet                 list add  entry getKey                      System out printf      s    d  n     entry getKey    entry getValue                          for        System out println  Duplicate elements   gt      list           fix     Example 2   using Arrays stream   in Java 8  public class a37       public static void main String   args            String aa    Protijayi Gini           String   stringarray   aa split           Map lt String   Long gt  map    Arrays stream stringarray           collect Collectors groupingBy c - gt  c   Collectors counting              map forEach   k  v  - gt  System out println k          v

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public static void main String   args            String name  AnuvratAnuvra           char   arr   name toCharArray            HashMap lt Character  Integer gt  map   new HashMap lt Character  Integer gt              for char val arr                         map put val map containsKey val  map get val  1 1                               for  Entry lt Character  Integer gt  entry   map entrySet                  if entry getValue   gt 1               Character key   entry getKey                Object value   entry getValue                 System out println key       value

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If your string only contains alphabets then you can use some thing like this   public class StringExample   public static void main String   args        String str    abcdabghplhhnfl  toLowerCase           create a integer array for 26 alphabets         where index 0 1 2   will be the container for frequency of a b c        Integer   ar   new Integer 26          fill the integer array with character frequency      for int i 0 i lt str length   i              int j   str charAt i  - a           if ar j   null                ar j   1           else               ar j    1                            print only those alphabets having frequency greater then 1      for int i 0 i lt ar length i              if ar i   null  amp  amp  ar i  gt 1                char c    char   97 i               System out println     c    comes   ar i    times                           Output     a  comes 2 times    b  comes 2 times    h  comes 3 times    l  comes 2 times

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public static void main String args          char Char      int count      String a    Hi my name is Rahul       a   a toLowerCase        for  Char    a   Char  lt    z   Char              count   0          for  int i   0  i  lt  a length    i                  if  a charAt i     Char                    count                                    System out println  Number of occurences of     Char     is     count

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import java io    import java util    import java text    import java math    import java util regex     public class Solution        public static void main String   args            Scanner sc   new Scanner System in           int n   sc nextInt            String reverse1          String reverse2          int count   0          while n  gt  0                        String A   sc next                String B   sc next                reverse1   new StringBuffer A  reverse   toString                reverse2   new StringBuffer B  reverse   toString                if  A equals reverse1                                 for int i   0  i  lt  A length    i                                          for int j   0  j  lt  A length    j                                                  if A charAt j     A charAt i                                                         count                                                                        if count   2    0                                                A replace A charAt i                               count   0                                                          System out println A                             n--

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public static void main String   args            char   array    aabsbdcbdgratsbdbcfdgs  toCharArray            char     countArr   new char array length  2           int lastIndex   0          for  char c   array                int foundIndex   -1              for  int i   0  i  lt  lastIndex  i                      if  countArr i  0     c                        foundIndex   i                      break                                              if  foundIndex  gt   0                    int a   countArr foundIndex  1                   countArr foundIndex  1     char    a                else                   countArr lastIndex  0    c                  countArr lastIndex  1     1                   lastIndex                                    for  int i   0  i  lt  lastIndex  i                  System out println countArr i  0          countArr i  1

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In java    using for loop   import java util Scanner              author MD SADDAM HUSSAIN    public class Learn        public static void main String args               Scanner sc   new Scanner System in           String input   sc next            char process     input toCharArray            boolean status   false          int index   0          for  int i   0  i  lt  process length  i                  for  int j   0  j  lt  process length  j                       if  i    j                        continue                    else                       if  process i     process j                             status   true                          index   i                          break                        else                           status   false                                                                      if  status                    System out print      process index

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Map lt Character Integer gt  listMap   new HashMap lt Character Integer gt                                                     Scanner in  new Scanner System in                          System out println  enter the string                           String name in nextLine   toString                           Integer value 0                         for int i 0 i lt name length   i                                           if i  0                                                      listMap put name charAt 0   1                                                                               else if listMap containsKey name charAt i                                                                     value listMap get name charAt i                                                                    listMap put name charAt i   value 1                                          else listMap put name charAt i  1                                                      System out println listMap

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A better way would be to create a Map to store your count  That would be a Map lt Character  Integer gt    You need iterate over each character of your string  and check whether its an alphabet  You can use Character isAlphabetic method for that  If it is an alphabet  increase its count in the Map  If the character is not already in the Map then add it with a count of 1   NOTE  - Character isAlphabetic method is new in Java 7  If you are using an older version  you should use Character isLetter      String str    asdfasdfafk asd234asda       Map lt Character  Integer gt  charMap   new HashMap lt Character  Integer gt         char   arr   str toCharArray         for  char value  arr            if  Character isAlphabetic value                if  charMap containsKey value                    charMap put value  charMap get value    1                 else                  charMap put value  1                                    System out println charMap     OUTPUT  -   f 3  d 4  s 4  a 6  k 1

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Using Eclipse Collections CharAdapter and CharBag   CharBag bag        Strings asChars  The quick brown fox jumped over the lazy dog    toBag     Assert assertEquals 1  bag occurrencesOf  a     Assert assertEquals 4  bag occurrencesOf  o     Assert assertEquals 8  bag occurrencesOf        Assert assertEquals 1  bag occurrencesOf          Note  I am a committer for Eclipse Collections

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public class list        public static String name Character k           String s  the quick brown fox jumped over the lazy dog            int count 0          String l1             String l             List lt Character gt  list new ArrayList lt Character gt             for int i1 0 i1 lt s length   i1                 list add s charAt i1                      list sort null           for  Character character   list                l  character                    for  int i1 0 i1 lt l length   i1                  if  l charAt i1   k                    count  1                  l1 l charAt i1      Integer toString count                   if k                            l1  Space      Integer toString count                                  else                  count 0                                  return l1            public static void main String   args           String g   name               System out println g

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I solved this with 2 dimensional array  Input  aaaabbbcdefggggh Output a4b3cdefg4h  int     arr   new int 10  2       String st    aaaabbbcdefggggh       char   stArr   st toCharArray        int i   0      int j   0      for  int k   0  k  lt  stArr length  k              if  k    0                arr i  j    stArr k               arr i  j   1    1            else               if  arr i  j     stArr k                     arr i  j   1    arr i  j   1    1                else                   arr   i  j    stArr k                   arr i  j   1    1                                    System out print arr length       String output           for  int m   0  m  lt  arr length  m              if  arr m  1   gt  0                String character   Character toString  char  arr m  0                String cnt   arr m  1   gt  1   String valueOf arr m  1                     output   output   character   cnt                       System out print output

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sample Input   2 7 saska toro winn toro vanco saska toro 3 edddddd edddddd edddddd     sample output   4   1    import java util ArrayList  import java util Scanner   public class MyTestWhere                    param args             public static void main String   args            int count  line          Scanner sn   new Scanner System in           count   sn nextInt            sn nextLine                      for  int i   0  i  lt  count  i                   line   sn nextInt                sn nextLine                String numArr     new String line               ArrayList lt String gt  Arr new ArrayList lt String gt                 String first   sn nextLine                Arr add first  String f              for  int j   1  j  lt  line  j                      f  sn nextLine                    for int k 0 k lt Arr size   k                         if f equalsIgnoreCase Arr get k   break                      else if k    Arr size  -1   Arr add f                                                     System out println Arr size

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import java io    public class CountChar         public static void main String   args  throws IOException             String ch        BufferedReader br new BufferedReader new InputStreamReader System in          System out print  Enter the Statement           ch br readLine          int count 0 len 0          do                       try                       char name   ch toCharArray                  len name length                count 0                for int j 0 j lt len j                                       if  name 0   name j   amp  amp   name 0  gt  65 amp  amp name 0  lt  91    name 0  gt  97 amp  amp name 0  lt  123                           count                                   if count  0                  System out println name 0      count   Times                  ch ch replace    name 0                                       catch Exception ex                      while len  1                Output   Enter the Statement asdf23123sfsdf  a 1 Times  s 3 Times  d 2 Times  f 3 Times

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import java util Scanner       class Test                 static String s2             int l          void countDuplicateCharacters String Str                        String S Str toLowerCase                for int i 0 i lt S length   i                                  int k 1                  boolean value   repeatedCheck S charAt i                    if value  true                      continue                  for int j i 1 j lt S length   j                                            if S charAt i   S charAt j                           k                                                          System out println  character      S charAt i         k                    s2 s2 S charAt i                                     boolean repeatedCheck char ch                        l s2 length                for  int i 0 i lt l i                                  if s2 charAt i   ch                                        return true                                               return false                        public class Duplicacy            public static void main String   args                Scanner sc new Scanner System in               System out println  Enter any String                String s sc nextLine                Test t new Test                t countDuplicateCharacters s

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void Findrepeter        String s  mmababctamantlslmag       int distinct   0        for  int i   0  i  lt  s length    i               for  int j   0  j  lt  s length    j                   if s charAt i   s charAt j                                 distinct                                        System out println s charAt i   --  distinct           String d String valueOf s charAt i   trim            s s replaceAll d              distinct   0

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public class DuplicateValue        public static void main String   args             String s    hezzz            char   st s toCharArray             int count 0           Set lt Character gt  ch new HashSet lt  gt             for Character cg st               if ch add cg   false                   int occurrences   Collections frequency ch  cg                   count  occurrences                  if count gt 1                   System out println cg      This character exist more than one time                                      else                  System out println cg                                                      System out println count

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You could use the following  provided String s is the string you want to process   Map lt Character Integer gt  map   new HashMap lt Character Integer gt     for  int i   0  i  lt  s length    i        char c   s charAt i     if  map containsKey c         int cnt   map get c       map put c    cnt       else       map put c  1           Note  it will count all of the chars  not only letters

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public class dublicate    public static void main String   a        System out print  Enter the String        Scanner sc new Scanner System in       String st sc nextLine        int    ar new int 256       for int i 0 i lt st length   i                  ar st charAt i   ar st charAt i   1            for int i 0 i lt 256 i                  char ch  char i          if ar i  gt 0                        if ar i   1                                System out print ch                             else                               System out print ch    ar i

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There are three ways to find duplicates  public class WAP PrintDuplicates        public static void main String   args             String input    iabccdeffghhijkkkl            findDuplicate1 input           findDuplicate2 input           findDuplicate3 input               private static void findDuplicate3 String input             HashMap lt Character  Integer gt  hm   new HashMap lt Character  Integer gt              for  int i   0  i  lt  input length   - 1  i                  int ch   input charAt i               if  hm containsKey input charAt i                      int value   hm get input charAt i                    hm put input charAt i   value   1                 else                   hm put input charAt i   1                                   Set lt Entry lt Character  Integer gt  gt  entryObj   hm entrySet            for  Entry lt Character  Integer gt  entry   entryObj                 if  entry getValue    gt  1                    System out println  Duplicate      entry getKey                                         private static void findDuplicate2 String input             int i   0           for  int j   i   1  j  lt  input length    j    i                   if  input charAt i     input charAt j                     System out println  Duplicate is      input charAt i                                        private static void findDuplicate1 String input               TODO Auto-generated method stub         for  int i   0  i  lt  input length    i                   for  int j   i   1  j  lt  input length    j                       if  input charAt i     input charAt j                         System out println  Duplicate is      input charAt i

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This is the implementation without using any Collection and with complexity order of n  Although the accepted solution is good enough and does not use Collection as well but it seems  it is not taking care of special characters   import java util Arrays   public class DuplicateCharactersInString       public static void main String   args            String string    check duplicate charcters in string           string   string toLowerCase            char   charAr   string toCharArray            Arrays sort charAr           for  int i   1  i  lt  charAr length                 int count   recursiveMethod charAr  i  1               if  count  gt  1                    System out println       charAr i       comes     count     times                    i   i   count                else                 i                         public static int recursiveMethod char   charAr  int i  int count            if  ifEquals charAr i - 1   charAr i                  count   count   recursiveMethod charAr    i  count                     return count             public static boolean ifEquals char a  char b            return a    b            Output        comes 4 times  a  comes 2 times  c  comes 5 times  e  comes 3 times  h  comes 2 times  i  comes 3 times  n  comes 2 times  r  comes 3 times  s  comes 2 times  t  comes 3 times

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public static void findDuplicate String letter         for int i 0  i lt letter length   i                  for  int j i 1  j lt letter length   j                          if letter charAt i   letter charAt j                                 System out println letter charAt j                    break                                    findDuplicate  JAVA     The OUTPUT is   A

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class A    public static void getDuplicates String S        int count   0      String t           for  int i   0  i  lt  S length   - 1  i              for  int j   i   1  j  lt  S length    j                  if  S charAt i     S charAt j   amp  amp   t contains S charAt j                           t   t   S charAt i                                     System out println t          class B public class B    public static void main String   args       A getDuplicates  mymgsgkkabcdyy

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public class CountH        public static void main String   args            String input    Hi how are you            char charCount    h           int count   0           input   input toLowerCase             for  int i   0  i  lt  input length    i                   if  input charAt i     charCount                    count                                      System out println count

[java] Find duplicate characters in a String and count the number of occurances using Java

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