Find Duplicate Characters In String using Java

package com.zia.test;

import java.util.HashMap;
import java.util.Map;
import java.util.Set;

public class findDuplicateCharacter {

    /**
     * @param args
     */
    public static void findByusingMap(String str) {
        // HashMap with character and number of times they appear in given
        // String argument
        Map<Character, Integer> charMap = new HashMap<Character, Integer>();
        char[] charArr = str.toCharArray();

        for (char value : charArr) {

            if (Character.isLetter(value)) {
                if (charMap.containsKey(value)) {
                    charMap.put(value, charMap.get(value) + 1);

                } else {
                    charMap.put(value, 1);
                }
            }
        }

        Set<Character> charString = charMap.keySet();

        System.out.println("Duplicate Characters In =" + str);
        // set iteration
        for (Character ch : charString) {
            if (charMap.get(ch) > 1) {
                // If any char occur more than 1, printing it's count

                System.out.println(ch + " : " + charMap.get(ch));
            }
        }

    }

    public static void main(String[] args) {

        findDuplicateCharacter.findByusingMap("Hello How are You Doing?");
        findDuplicateCharacter.findByusingMap("Hope you all are doing good");
        findDuplicateCharacter.findByusingMap("Thank you very much for reading this");

    }

}

OutPut:-

Duplicate Characters In =Hello How are You Doing?
e : 2
o : 4
l : 2
H : 2
Duplicate Characters In =Hope you all are doing good
g : 2
d : 2
e : 2
a : 2
o : 5
l : 2
Duplicate Characters In =Thank you very much for reading this
e : 2
a : 2
n : 2
o : 2
h : 3
i : 2
u : 2
r : 3
y : 2

Its very simple program no need to explain,get the character array from String, iterate through that and put it in a Map with character and their count.Then get a Set containing all keys of map and iterate through Set and print characters which have appeared more than once.
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