Java program to check frequency of characters in a string

October 14, 2022

Check Frequency of Characters in a string

Finding the frequency of a character in a string, means we have to check how many times a particular character is present in that string. Here, we have coded a Java Program for the same. Let’s take an example of a string “prepinsta” . In which we have to check that how many times each of the characters gets repeated in the string.

 

Java program to check frequency of characters in a string

Algorithm

  •  Take string input from user and store it in the variable called “str”.
  • After that make freq array having size of length of string.
  • Convert string to char array .
  • Run for loop start from i=0 to str<length() store 1 to freq array.
  • Run j loop start from i=i+1 to j<str.length().
  • check condition if(string[i] == string[j]) then do freq[i]++  and set string[j]=’0′ .
  • After that display frequency of character one by one.

Code in Java (Check Frequency of Characters)

import java.util.Scanner;

public class FrequencyOfCharactersInAString {
   public static void main(String[] args) {
    Scanner sc =new Scanner(System.in);
     System.out.print("Enter String : ");
     String str = sc.nextLine(); 
     int[] freq = new int[str.length()]; 
     int i, j; 

     //Converts given string into character array 
     char string[] = str.toCharArray(); 
     for(i = 0; i <str.length(); i++) { 
        freq[i] = 1; 
          for(j = i+1; j <str.length(); j++) { 
            if(string[i] == string[j]) { 
            freq[i]++; 

           //Set string[j] to 0 to avoid printing visited character 
            string[j] = '0'; 
          } 
       } 
    } 
    //Displays the each character and their corresponding frequency 
    System.out.println("Characters and their corresponding frequencies"); 
    for(i = 0; i <freq.length; i++) { 
       if(string[i] != ' ' && string[i] != '0') 
          System.out.println(string[i] + "-" + freq[i]); 
       } 
   }
}

Output

Enter String : prepinsta
Characters and their corresponding frequencies
p-2
r-1
e-1
i-1
n-1
s-1
t-1
a-1
 
 

Toggle each character in a string

Count the number of vowels

Length of the string without using strlen() function

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16 comments on “Java program to check frequency of characters in a string”


  • Abhishek

    public static void main (String[]args)
    {
    HashMap map = new HashMap();
    String str = “prepinsta”;
    char ch[] = str.toCharArray();
    for(Character ch1 : ch){
    map.put(ch1, map.getOrDefault(ch1, 0)+1);
    }
    System.out.println(map);
    }
    }


  • Shekhar Suman

    String str=”prepinsta”;
    Map hm=new HashMap();
    for (int i=0;i<str.length();i++){
    char ch=str.charAt(i);
    if(hm.containsKey(ch)){
    hm.put(ch,hm.get(ch)+1);
    }else{
    hm.put(ch,+1);
    }
    }
    System.out.println(hm);


  • ARYAN

    import java.util.*;
    public class Main
    {
    public static void main(String[] args) {
    String str=”my name is aryan kumar saw”;
    HashMap map=new HashMap();
    for(int i=0;i<str.length();i++){
    char c=str.charAt(i);
    if(Character.isAlphabetic(c)){
    if(map.containsKey(c)){
    map.put(c,map.get(c)+1);
    }else map.put(c,1);
    }
    }

    System.out.println(map);
    }
    }


  • Trinadh Kamaparapu

    import java.util.*;
    public class Frec
    {
    public static void main(String[] args)
    {
    String str =”TrinadhNaidu”;
    str=str.toLowerCase();
    char test[] = str.toCharArray();
    int n = str.length();

    Map a = new HashMap();

    for(char c:test)
    {
    if(a.containsKey(c))
    {
    a.put(c,a.get(c)+1);
    }
    else
    {
    a.put(c,1);
    }
    }

    for(Map.Entry m:a.entrySet())
    {
    System.out.println(m.getKey()+” “+m.getValue());
    }
    }
    }


  • Tridip

    import java.util.*;
    public class Frec{

    public static void frechar(String str){

    char test[] = str.toCharArray();
    int n = str.length();

    Map a = new HashMap();

    for(int i=0 ; i<n ; i++){

    if(a.containsKey(test[i])){

    a.put(test[i],a.get(test[i])+1);
    }
    else{

    a.put(test[i],1);
    }
    }

    for(Map.Entry p :a.entrySet()){

    System.out.println(p.getKey() +”Occurs” + p.getValue());

    }

    }

    public static void main(String[] args){

    String str =”Tridip”;

    frechar(str);

    }
    }


  • Palak Gupta

    public static void checkFrequency(String str) {
    String[] freq = new String[str.length()];
    boolean[] counted = new boolean[str.length()];

    for (int i = 0; i < str.length(); i++) {
    int count = 0;
    if (!counted[i]) {
    for (int j = i + 1; j < str.length(); j++) {
    if (str.charAt(i) == str.charAt(j)) {
    count++;
    counted[j] = true;
    }
    }
    freq[i] = String.valueOf(str.charAt(i)) + String.valueOf(count + 1);
    }
    }

    for (int k = 0; k < str.length(); k++) {
    if (freq[k] != null) {
    System.out.println(freq[k]);
    }
    }
    }


  • Akhilesh

    package com.prep.strings;

    import java.util.HashMap;

    public class FrequencyAkash {
    public static void main(String[] args) {

    // char [] arr = {‘a’, ‘k’, ‘h’, ‘k’, ‘s’ ,’d’}; OR
    String name = “aeiouieaeeee”;

    char [] str = name.toCharArray();

    HashMap map = new HashMap();
    // int count = 1;

    for(int i=0; i<name.length(); i++) {
    int count = 1;

    for(int j=i+1; j<name.length(); j++) {
    if(str[i] == str[j]) {
    count++;
    }
    }
    map.putIfAbsent(str[i], count);
    // count = 1;
    }
    System.out.println(map);
    }
    }


  • Srinjay Kapri

    import java.util.*;

    class jp {

    public static void main(String[] args) {
    String s=”prepinsta”;
    HashMaphm=new HashMap ();
    for(int i=0;i“+hm.get(ch));
    }
    }


  • theeksh18

    package practice;

    public class Top100 {

    public static void main(String[] args) {
    // TODO Auto-generated method stub
    String string=”prepinsta insta”;
    String s =””;
    char arr[]=string.toCharArray();

    for(int i=0;i<arr.length;i++) {
    int c=1;
    for(int j=i+1;j<arr.length;j++) {
    if(arr[i]==arr[j])
    {
    c=c+1;
    arr[j]=0;
    }

    }

    if(arr[i]==0)
    continue;
    System.out.println(string.charAt(i)+" appears "+c);

    }

    System.out.println(s);

    }

    }


  • Ankitha

    public class FrequencyOfChar {
    public static void main(String args[]) {
    Scanner sc = new Scanner(System.in);
    String str = sc.nextLine(); char ff=’ ‘;int count=1;
    char[] strc= str.toCharArray();
    Arrays.sort(strc);
    for(int i=0; i<strc.length; i++) {
    count=1;
    if(ff!=strc[i]) {
    ff=strc[i];
    for(int j=i+1; j”+count);

    }
    }

    }

    }


  • Vivek

    static void countFrequency(char[] c){
    HashMap map = new HashMap();
    for(int i = 0 ; i<c.length ; i++){
    if(map.containsKey(c[i])){
    map.replace(c[i],(map.get(c[i])+1));
    }
    else
    map.put(c[i],1);
    }
    System.out.println("Iterating HashMap");
    for(Map.Entry m : map.entrySet()){
    System.out.println(m.getKey()+" "+m.getValue());
    }
    }
    public static void main(String[] args) {
    System.out.println("Enter String");
    Scanner sc = new Scanner(System.in);
    String str = sc.nextLine();
    countFrequency(str.toCharArray());
    }


  • Mahesh

    import java.util.*;
    public class Main
    {
    public static void main(String[] args) {
    String s=”prepinsta”;
    Mapmap=new HashMap();
    for(int i=0;i “+entry.getValue()+” “);
    }
    }
    }


    • Mahesh

      String s=”prepinsta”;
      Mapmap=new HashMap();
      for(int i=0;i “+entry.getValue()+” “);
      }