Write a program to count the frequency of each and every character of a string by using collection classes.

package com.javahelp.stringprog;

import java.util.HashMap;

import java.util.Iterator;

import java.util.Map;

import java.util.Scanner;

import java.util.Set;

public class CharFrequencyCount {

public static void main(String[] args) {

Scanner sc=new Scanner(System.in);

String s=sc.nextLine();       // enter the string

HashMap<Character, Integer> hm=new HashMap<Character, Integer>();

int count=0;             // variable to store count value

for(int i=0; i<s.length(); i++)

{

                        // check charcter exist in map or not

if(hm.containsKey(s.charAt(i)))          

{

count=hm.get(s.charAt(i))+1; 

// get the value of map and then store it again with increment by 1

hm.put(s.charAt(i), count);

}

else

{

count=1;

                               // new character add in map with count value 1

                              

                               hm.put(s.charAt(i),count);

}

}

                     // to iterate the hashmap convert hashmap into set

                  Set set=hm.entrySet(); 

Iterator it=set.iterator();

while(it.hasNext())

{

                     // set elements return entry value so typecast with enty

                          Map.Entry entry=(Map.Entry) it.next(); 

System.out.println(entry.getKey()+" "+entry.getValue());

}

}

}