Java Program to Find Duplicate Character from a String and Count of repetition

Java Program to Find Duplicate Character from a String and Count of repetition thumbnail
By Dhiraj ray 31 December, 2017


While dealing with string, many of the time it is required to find or remove duplicate character from a string.Following is the java program to find duplicate or repeated characters from a given string.The program also results the cont of the duplicate characters.

package com.devglan;

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

public class DuplicateChar {

    public void findDuplicateCharsInString(String str){

        Map map = new HashMap();
        char[] chars = str.toCharArray();
        for(Character ch : chars){
                map.put(ch, map.get(ch)+1);
            } else {
                map.put(ch, 1);
        Set keys = map.keySet();
        for(Character ch : keys){
            if(map.get(ch) > 1){
                System.out.println(ch + " -- " + map.get(ch));

    public static void main(String a[]){
        DuplicateChar duplicateChar = new DuplicateChar();


As we know, HashMap implementation in java holds key value pair and it does not provide duplicate keys, here in the program we have used hashmap to hold the different character of a string and whenver a key already exists in the map simply increase the count of the hashmap value.At the end we can get the duplicate character whose hashmap value is greater then 1 along with the repeated count of the character.


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