Hashmap implementation to count the occurrences of each character

import java.util.HashMap;
import java.util.Map;
...
Map<String, Integer> freq = new HashMap<String, Integer>();
...
int count = freq.containsKey(word) ? freq.get(word) : 0;
freq.put(word, count + 1);

Hai All The below code is to count the occurrence of each character and it should print the count. may be helps you..Thanks for seeing

package com.corejava;

import java.util.Map;
import java.util.TreeMap;

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

        String str = "ramakoteswararao";

        char[] char_array = str.toCharArray();

        System.out.println("The Given String is : " + str);

    Map<Character, Integer> charCounter = new TreeMap<Character, Integer>();

        for (char i : char_array) {

    charCounter.put(i,charCounter.get(i) == null ? 1 : charCounter.get(i) + 1);

        }

    for (Character key : charCounter.keySet()) {
  System.out.println("occurrence of '" + key + "' is  "+ charCounter.get(key));
        }

    }

}

Java 8 streams:

Map<String, Long> map = 
    Arrays.stream(string.split("")).
    collect(Collectors.groupingBy(c -> c, Collectors.counting()));

Guava HashMultiset:

Multiset<Character> set = HashMultiset.create(Chars.asList("bbc".toCharArray()));
assertEquals(2, set.count('b'));

You're leaving char ch set as the same character through each execution of the loop.

It should be:

ch = char_array[i]; 
if(charCounter.containsKey(ch)){
     charCounter.put(ch, charCounter.get(ch)+1);
}
else
{
    charCounter.put(ch, 1);
}

Inside the for loop.